I'm kinda late to this thread but I don't visit often enout to stay up with the times. I fly both in multiple plames and prefer the McCoy. McCoys pull a few hundred rpms higher (static on the bench) with the same prop, fuel, plug and don't burp in the air. Both start the same whether hot or cold. Overally, the Fox is a close 2nd and survives lean runs better...but burps.
Finally got a chance to do some flying with the revised ship. I have been trying to use 4S 3300 mah packs instead of 3900 mah packs, this save about 1 1/2 oz. Problem was that the 3300 pack was strong until about the first loop on the clover. I have found some Zippy 4S 3700 mah packs that are thin and only about 3/4oz heavier than the 3300 mah TP packs at 1/3 the price. I flew them today and all the mods worked great. There was a bit of a breeze so it was a good test to see how the ship handled the maneuvers up top. It was just as I hoped for, no kitting, presented nicely and traced solid. All in all a success.
Don't get your expectations up too much about an upright mount. I tried four different vintage Fox 35s (50s,60s,70s,80s) with and without hemi and stuffer in the upright config. All burped same as a profile side mount...virtually no difference. That was using both flat and tapered nv. All spray bars were 2 hole. 5% & 10% nitro/25% & 29% castor + various hot plugs. I don't think any of those have anything to do with it though. Like said already, stuff the bipass with a stick and be done with it.