I can only add to this that Andrew from CMDR Arithon from
http://www.elite-dangerous-blog.co.uk/ managed to get official answer from FDev and it is as it goes:
GU-97 Imperial Fighter 10 t
F63 Condor 20 t
XG7 Trident 20 t
XG8 Javelin 20 t
XG9 Lance 20 t
Taipan 22 t
Honestly, I'm not sure how I feel about the 'canon' SLF masses. When I made my estimate of the mass of SRVs and SLFs earlier in this thread, I went on the assumption that the module mass listed in outfitting for vehicle hangars included the mass of the modules itself and the mass of the vehicles they contained and that the game engine's current limitations prevent the game from changing the module's mass when some/all of the vehicles are not present in the ship. For example, a size 7 fighter bay carries 30 SLFs (including the parts to 'print' new ones) and has an all-up mass of 60 tons, thus it would make sense for every available SLF to have a mass of <2 tons (probably closer to 1 ton if the different sizes of modules have quasi-proportional mass increases).
Obviously, this is not the case. Somehow the size 7 fighter bay can hold up to 660 tons (30 Taipans at 22 tons each) of SLFs and SLF parts in a module slot that is limited to 128 tons of cargo, all while having a
total mass of 60 tons. Forget the Anaconda's hull being made of unicorn farts, there's a new king of breaking the physical laws of nature in town in the form of the mass-vanishing fighter bay.
That said, the canonical SRV mass of 4 tons kinda makes sense (even if it seems a bit high to me). There is no SRV bay that has a mass lower than the total mass of all of the SRVs it can carry, although attributing the remaining mass to the module itself leaves a rather interesting mass curve that sees the mass of larger G-rated hangars get smaller (2G - 2 tons, 4G - 2 tons, 6G - 1 ton), although this isn't really a problem for the H-rated hangars (not that anyone ever uses them to my knowledge).
The main saving grace for the SRV is that unlike the fighter bay, the SRV bay DOES NOT carry additional rebuilds, therefore not having to carry the additional mass that the rebuild(s) would require. I suspect that the SLF masses were chosen with the idea that the fighter bay would not be able to print new fighters. This would go a long way to making the fighter bays
somewhat realistic, as the only way the mass of the fighters carried would exceed the listed mass of the module would involve carrying at least one Taipan (with the additional condition of NOT taking an imperial fighter in the case of the size 6 fighter bay). Perhaps it is time for the whole 'SLF rebuild' idea to be thrown out and for SLFs to get buffed to the point where they are no longer dime-a-dozen NPC distractions instead....