I was looking for something and happened to run across this. It's a 306cc motor that BFA have put together for SIP.
Takes a BFA 306 top end.
$1,300 for the cases and another $1,100 for the cylinder, but it's standard P200 parts other than that.
They also make versions of the cases which are reinforced and pre-matched to the Malossi MHR 221, standard PX150, and P200.
They're saying 60 HP potential out of the gate, and it looks like it'll be a bit cheaper than building out a comparable Pinasco 250, too.
(I had a chance to inspect the first 250 that came into the US at Scooterworks back before the holidays. I wrote up some notes on it, but overall, I was impressed with the quality of the parts from both a design and build perspective. They're saying ~30 HP in the stock configuration, but with 50 or so possible, and lots of proprietary components)