What is the purpose to flip the diffs? Does this make it stronger?

No. The ONLY reason to flip the diffs is if you are using a sensored brushless system (ie., Novak) and the motor runs backwards. On non-sensored systems, you can switch the pos/neg motor wires to make this correction.

Have you decided on a BL motor?

I am thinking the 9xl with a mm

No need to flip diffs - will work best on 4s - get a UBEC, RCM heatsink and 3x25mm fans.

Any hints on how to get fans attached to Mikes Feigao heatsink ?

I think people use 40mm fans with M3 screws that just bite inbetween the fins on the heatsink slightly. Seems to be the usual way I see in pics, otherwise I have seen one or two secured with long zip-ties wrapped around the motor,heatsink & fan.

I just used 2 20mm 5v fans and some self tapping wood screws... Worked a charm/

Thanks guys.

well I might not be putting on the brushless set up on my e-revo I have the feigao 9xl motor but no esc yet but my cousins neighbor wants to trade me for his 1/6 monster buggy with a 23cc zenoah weed whacker motor:lol: and tuned pipe very tempting I always wanted one but they are too much from the get go... maybe down the road I will do another one I just love how easy it was to work on and build

well he did not want to go threw with the deal so now I am looking for a good brushless motor,esc, and battery set ups also for batteries no lipo even though they are the best option :yes: