i'll leave this to the experts but [bore you] with a couple of experiences. Had a procircuit [or similar] on my RT1 & perked it up well for a standard motor, have an RT3 cylinder on it now & is 'too' pipey compared to RT1. Story2--same RT1 had an RT2MX top end & was fast using DT1 GYT pipe, [not sure where i put that!!], then oneday i fitted a RH pipe of a road going RZ350 twin, tapered header & what you'd think would be a strangled tail baffle & it transformed it into having lots of low down plus same heaps up top & a linear power all the way up. had to slightly straighten the header a bit & think it had a spigot bit i hooked out at the port [start] of pipe. 20 years ago or more but 'the most strange & unlikely things work sometime. Had that RZ [or was it RD350LC] pipe on the RT1 ride to work bike & was very good & [quiet too]. Also had a 400cc IT cylinder'd [thing] that was hopeless but revved crazy & found someone had ported it to 190 degrees exhaust duration so just took a guess & add 100mm [4 inches] to the header & transformed in to useable power. Thanks. ps, made about 10 pipes for my 'Bucket Racers' [miniature road racing], suzuki mudbug [or ts100] based & motors & same story--as in sometimes the most unlikely things work. Have a set of cardboard templates i used to use & then spun some wooden tapers up to drive into the welded section to make the shape better after welding. Long [sometimes sad] story, but success too. Sorry if this is 'No' help at all but got it off my chest anyway. Cheers. [if i'm on the right track] just love your RT1 i saw the pics of up here somewhere.