Re: my bike poll
Dude nice bike! Is that a 26"? I believe you could get away with an in frame set-up, yes.
I would go with a slant head just to be sure. I have built two 24" Mtn. bike builds, and I had to use a short spark plug on my first one. Due to clearance issues with the Top bar. I have had no such problems with the slant head though.
Hope it Helps. I am also a proud member of the 20 MPH. club