I've seen others on the boards here ask this question and I had the same question myself: What size does 1/100 and 1/144 scale Gundam model hands equate to for my Transformers? I'm primarily focusing on MP's so my perspective will be from that line. 1/144 scale is about the size of MP-21 Bumblebee's hands. What do you get with the set? You get two sets of non-articulated hands, with three poses each: closed fist, trigger/holding gun, and open with fingers spread. 1/100 scale is about the size of the Fan Style hands for MP-17, MP-18, and MP-19. What do you get with the set? You get two sets of non-articulated hands, with three poses each: closed fist, trigger/holding gun, and open with fingers spread. They're really detailed and look good. I image for customs the open hand probably won't be of much use as transformation would become hindered.
This is something I've looked into as well. For those who need the info in non-MP terms, 1/144 hands work for well deluxes and 1/100 hands fit well on voyagers.
What kind of fully articulated hands should I use to replace the originals from the TLK leader Megatron?
These seems to be just regular HG 1/100 and 1/144 hands, so yeah. I don't think Bandai ever sells the MG hands on their own, but Hobbybase does. 1/100 Mechanical Hand 100 Square Dark Gray
I think those are the ones I've used recently. They're quite nice, but can be problematic. They are articulated straight from the sprue, so no assembly of the fingers is required. The downside is the connection to the actual hand is weak, consisting of a thin c-clip that attaches to a tiny post mount. They easily loosen up, and won't hold 5mm weapons easily or at all. Also, the fingers require either longer fingernails or tweezers to move the pre-made joints. Kind of sucks in that moving the fingers can stress the base c-clip. Catch 22. Overall, they're good for posing but that's about it.