[ In advance: here is a warning! : LONG POST HERE! 
As I thought it best to explain our level of knowledge (ignorance?! LOL! 
) here, & the key facts re us & our issue - so they're at hand to all. No point hiding ignorance as that way people learn nothing! 
]
Thanks for your help to Trev & all. We have had not had a chance tp look into this
much since last posted: it's been a busy June/July doing outdoors jobs - in between the rain clouds!
Re your various queries:
1.
A HD T2 not an HDR T2. That explains some of my queries. Didn't notice that.
Answer: I have just checked & yes it
is a Humax
HDR-FOX T2. The model no. is conveniently printed on the front of the Humax! So no need to scrabble around trying to look at the back of the box/TV, inadvertently disconnectin leads etc!
2.
Q1. What size internal drive do you have already?
Answer: The internal drive is whatever the size that the Humax manufacturer supply with this HDR-FOX T2; i.e. I presume there's a standard size suppliued with the unit. We haven't made any changes to any internal parts of the Humax, as per our earlier post:
Re "fit a larger HDD into the Hummy": with our current minimal techy-knowhow - such a DIY job is way out of our Hummy skills!
3.
OP doesn't appear to be familiar with the Custom Firmware
Answer: No, we're not! So we're going to look into the various URLs that Black Hole supplied. That should take some time looking into. Maybe some lengthy reading/research time is required, inside the house, aided by this rainy July weather I hope! ,)
4.
Surely it would be 'better' and less confusing with just one big USB HDD
Answer: We don't want
multiple external drives; the reason we have so many is just to have lots of external storage
space external to the Humax itself. Further to our earlier post:
we looked into this a year or so ago & thought (?!) that we had read that a large external USB drive couldn't be supported by the Humax we own. Maybe we were wrong with that research?
I have double-checked this data we had read, & confirmed that we had notated that we had read (though hadn't notated
where we had read this - oops!) that a > 2TB external USB drive couldn't be supported by the HDR-FOX T2, i.e.
an external drive was limited to a maximum size of 2TB.
We therefore opted instead to use
several 2TB external drives, connected by a USB hub. That way, we can store up to 5 x 2TB = 10TB of stored data/films/programmes. This we hoped would be a solution to a 2TB limitation! Sadly, it appears not!
Obviously, if we
can in fact use just 1
very large external drive (a drive giving us e.g. > 8TB or > 10TB storage space), that would be a far better option!
So,
is that an option??
[Bit of history as to why we own & how we use a Humax:]
We bought the Humax as we wanted to both:
(i) record lots more TV progs & films (more than we could with our BT Vision+ box)
(ii) then have the option to save them externally, for future viewing
Our BT Vision+ box - which was the only DVR that we owned pre buying the Humax - didn't offer (a) much internal space (b) any save-externally option as it just offered a record-to-internal-drive option.
(BTW, we still own that BT Vision+ unit, but will probably be getting rid of it soon: we used to use it - after we bought the Humax - as a backup recorder e.g. at Christmas time's busy TV schedule, but haven't used it for months. So it's using up space under the TV.)
So we want to use the Humax to its maximum potential.
We have all 5 external drives left plugged in to the Humax so that we can either free space from the Humax by moving data/videos onto an external drive, or watch a video directly from one of those external drives.
In other words, any external drive is used to form an
accessible library of videos! It also acts as a back-up location for any files we really don't want to lose.
5.
Surely it would be 'better' and less confusing [...] or fit a larger HDD into the Hummy?
Answer: If we
are correct in our previous research that a > 2TB external USB drive can't be supported by the HDR-FOX T2, then maybe this is the only next option.
I have now read more posts in this thread - & at
Multiple USB Discs on the humax at the same time - thanks for that MontysEvilTwin - re 7-port USB hubs, saying they're a non-option!! So sadly it appears there
is a limit to the number of external drives e.g. to a total of 4 x 2TB.
So still need to know if 1
very large external drive (a drive giving us e.g. > 8TB or > 10TB storage space) is an option.
Re increasing the capacity/storage limit of our Humax unit:
In any case, any such change to the internal drive would surely only be a partial solution to our problem, as it would only increase the
internal space, not the space on an
external drive which is what we really want. Unless, of course,increasing the internal space makes it possible to increase the
external space too . . . ?!
The only thing is: if we
can , we'll do so as long as there is a shop or some tech-bod out there with someone who can do this for us. This kind of techie-stuff is the sort of thing we always pay someone else to do, in either money or beer! ,)
I do gather that :
there is plenty of expertise here to help if you are up to using a screwdriver and a bit of common sense
but I'd hate to RELY on what we had done, & mess it up. I'd always think if the Humax blew up it would be our fault!
I's rather rely on someone whose expertise is this area of gadgets. Maybe in 6 months or so we'll feel we have sufficient technical know-how & are brave enough to try it ourselves, but not yet!
YIKES!!!! THERE'S SO MUCH TO LEARN!!!!
(tongue-in-cheek comment!)