Curious as to what fan you are now using. I have had very good luck with the stock set-up in both my T33's. But I fly at a small field and really can't use a lot of high speed. I was using 8 cells and had about 150 flights on the motors before I noticed any performance reduction. Using the 2S2p LiPo's will be a good step as the weight of the drive drops.

I have re-used the Ky fans in two of my own design projects. My F9F and F86 both fly very well with these fans driven by HET 2W motors on 2S2Px4200 LiPos

I believe K&A models sells an L39 that will accept the Ky Fan


http://www.kamodels.com/