I'm not Randy, but I'd say that in general if you make such a large change in the engine layout you'll need to make a change in the cooling system to match.  As to specifics -- I dunno.  My first inclination would be to follow basic principals (make lots of low-velocity air flow past the cooling fins and the exhaust pipe), or to look at a bunch of planes with similar engines, figure out which ones seem to cool well, then ask the owners if you can look at how the cooling air is managed.  If you can find magazine plans that detail this -- good.  Look at 'em.

Dennis,

I have always been told to have the rear opening at a minimum twice the diameter of the front.  I would think 3-4 time the area and make sure you have good flow around the muffler and you'll be fine.

James

Thanks Jimmy, did you put any sort of air deflectors under the tank floor or just leave that area open?

BTW, I had a trim problem.  After I changed tip weight and forgot that I had changed it because at first it flew really well, the best flying plane I've ever had, two crashes took off landing gear, then finally remembered I had changed the tip weight from 1 oz in the box to 3/4 oz and had bad problems in hard turns.  Finally I checked tip weight box and found that I had changed it and forgot.  Now I have 1 1/2 oz in the tip weight box and flies great! Put plenty of tip weight to start with.  This is what worked for me anyway.   Yours may differ.

-Jimmy

Winter has arrived so it's back to building. I did more work on my Jaguar following the advice previously given. Thanks a bunch guys.