Hey Rhino,
Don't worry about the oomph of a 290 it is an easier bike to ride than the 250 (IMHO).
All of the Shercos I have owned have been very tune-able(de-tune-able?) according to how you set the timing.
Don't despair about getting rid of your Scorpa ,as you pointed out you will still have a use for it....just hitch it up to that muck-spreader on the farm and it will be in it's element!! O-arhh-o-arhh
Cue:-Bombing run from the Scorpa owners club