The 17.5 is fantastic.

I changed my mind and went straight to 5.15 FDR before I even ran it once, glad I did, and I didn't change it all night. I moved the timing to 45 degrees on the can. Measured 50c motor temp after 5 minutes. I think it could take another tooth pretty easily, that'll make it 4.98 FDR, It has plenty of punch as it is now.

Cleared our triple which is 6m crest to crest (according to google maps, doesn't look that far IRL). Our straight is 27m with a 180 degree sweeper at the end that is flat in 4wd stock, effectively doubling the straight length.

Managed third which is ok given my first attempt in stock (I was turning into pipes all night, too used to a 6.5 in this buggy), fastest lap was the quickest of the night for 4wd stock by 4 tenths.

Weight is 1697 with a fan and sweep tendroids, I'll run it Sunday at a track where I use schumacher mini spikes, that's 50g straight away from tires alone. Need a shorty conversion though.

All in all, it's a great motor, glad I chose it.

Volition, make sure you run your belts really really really loose on that cat for stock.