The pro's are if you get it right, the reduction of much vibration.
The con's are if you get it wrong much much much more and worse vibration.
I had great success using Hayes beam style isolation mounts when used on a GP UDO 46 and a Saito FA82. It took all the drumming of the covering out. Turned it into a pleasure to fly.
Each airplane/engine combo will need a slightly diferent type of isolater. The experimenting and finding success is the fun part for me. If you dont want to spend a bunch of time experimenting try the hayes mount.
If all else fails switch the conversion parts over to a Echo 45cc engine. There won't be any more vibration.