From memory, I think the standard 2L Bosch starters were either 0.8(maybe 0.9?)HP for the short one & maybe 1HP for the slightly (about an inch?) longer version.
I grew tired of replacing starters all the time (about four of them in 6 years I think, one of those was reconditioned too & only lasted just beyond it's 12mth warranty).
The higher the compression the less the starter will like it, that's for sure, but I've no idea on limits as such.
The best thing I ever did as far as starter motors go was ditch the factory unit & install a gear reduction one.
Bought it from "Rally Design", though you can get them elsewhere, it's a Powerlite unit - model #RAC110A.
This is it :
http://www.rallydesign.co.uk/product_info.php?products_id=13703 Cheers, Jason.