I think its very easy imo,

been speaking to a good few people in the know and they have done a few similair conversions, one person did a st170 engine on bike tbs and got 260 odd with fairly straight forward modification.

What similar conversion have you seen only 180bhp on as i would be gutted if it was me? crazycage off here has done a tb and ms conversion on a st170 mapped by unicorn dev. (rick) which has responded really well, hopefully going in it in december to see how it goes, funny enough I have just got my invoice for my pistons whilst typing this :-(

from what ive learnt with a cr of about 11/1 tbs and some porting you would struggle to get less than 210