The nice thing about the 35RA in this installation is it's compact dimensions - due to the fact it comes with rear exhaust. If you get the 30, you'll need an aftermarket wrap around Pitts type to keep from hacking the cowl up to bad. The popular one there is by Jtec, which is 90 bucks or so.
When you add the 90 bucks to the price of the 30, the value of the 35RA becomes more apparent?