both are rated for 8hp!
the TAV2 kit as well as the series 30 without it's backplate and jackshaft.
the misconception struck me too since there is a typo on hoffcocomet's homepage claiming the series30 to handle 13hp (I don't know where you got the 15 from tbh...)
Anyways, the manual clearly states 8horses as well!
That being said:
the issue is the belt or say lack thereof
to transfer the assumed torque (and that's the main issue) of an engine with more than 8 horses, the belt would need a bigger flange mainly to provide enough contacting surface with the sheaves.
Since by improving the power of an engine (mainly by means of higher rpms for industrial engines like yours) you do not improve the torque too much to be affected really.
if you go for higher compression ratios impoved cam profiles (for torque not speed) and the like, you will certainly decrease the mileage of your belt..
but from what you see on this forum, many engines around here run a Tav2 kit w/o issues, some push 10 or more horses.
And we even have supermanotorious who installed a TaV2 on his 13hp 420cc predator engine
without shredding the Tav to pieces
(it's a winch setup.. still more torque than a 240cc engine would provide
)
In short:
So yeah, engine nominal 8hp...
the Tav2 kit should serve you well, no worries!
'sid