Draw lenght increase means arrow lenght increase...
Your brothers arrows will have more weight and with this also goes a different "front of the centre" so the tips weight will also increase (just guessin'). Most energy you gain by more draw lenght will be "taken" by the new, heavier arrows... There is no doubt with the same arrows set for 28.5" it would shoot faster by >20 fps but thats unlikely to be managed (don't tell me you shoot 31" arrows from the start
). I would guess a 10-15 fps increase with "same quality" arrows and a noticable force increase
.
Note, that I don't realy have much knowlege about how Tomkat behaves in this case.
There might be even less fps increase (you would wonder how many factors change
) using the "same" arrows...
Basicaly, more draw = more speed
...how much more, is not a relevant question[:@].
Do it, test it, post it
. At least, when someone else asks next time the same thing, you will be a HERO
.