It's my opinion that Fibreskyn heads dampen the sound too much and make the drums sound dead. I've tried Renaissance heads on my '70 Ludwig kit, and I liked the sound of coated ambassadors better! Maybe it's just me.
I've tried Fibreskyn, Renaissance, Emperor (clear and coated), G2, Ambassador (clear and coated), G1, Pinstripe, Hydraulic, Reverse Dot, EC2, and Pearl Protone heads on my 12" and 14" toms, and the coated ambassadors sounded the best for bringing out the warm woody qualities of the drums, IMHO.