OP : I don't see the point of them for Asps, never needed one in over 100K LY of exploring.
Like an Anaconda owner earlier in this thread I've used one to drop my Asp from 32 tonnes to 24 tonnes which increased my range a little bit. I tried it out on a quick 200 jump test trip and it worked fine, 24 tonnes gives me 5 full distance jumps which is quite enough, just having 16 tonnes would allow only 3 full distance jumps which I would not be comfortable with.