My suggestion would be to open up the live map on the smp2 wilderness, and zoom out to see if anyone has uncovered a mushroom biome island chunk. It may be the fastest way without having to search the seas by boat.
Hey ya. Ya I had been trying that, and then switching to terrian view, but im not really sure what it will look like on the big map, and cuple i did sail out to ended up not being what iw as looking for. but yes, this is a valuble tool that i will continue to utilize in my search.
They are normally large rounded islands with a few big red circles on them, (which should be giant mushrooms unless someone has harvested them) They should be a pinkish/purplish colour too I imagine