Thats the kind of stuff that i like. Used to own a GSXR7/11 along time ago...totally uncontrollable 100+ big sweepers was like riding a rocking horse....
The 851/888/926 Corsa's made around 136 rwbhp at the end of their development and they were finding the limits of the chassis/frame and swinging arms. Swinging arms mounted to the rear of the C/cases caused them to crack. 160+ rwbhp will tie the frame in knots if used to it's maximum. There's been quite a few 851/1098's built and this's not one of the better ones. The support/mounting of the swinging arms needs to be addressed, in a similar way to the later 9*6 or 1098 chassis with outrigger supports.
It's a nice build, (granted I wouldn't have done it like that) but you can tell it's been built by a mechanic and not a builder of bespoke custom stuff. I'd hate to know what was charged all said and done for that build. 300hrs labour doesn't come cheap in anyones book.