Next time, don't use white metal whatsoever for Sherman based vehicles. The benefit of Fruils and Space Ace etc is their ability to impart the drape of weighty links. Shermans had "live tracks" that would show no sag in a running vehicle. Otherwise, there was a huge risk of throwing a track.
Now, you're faced with keeping the upper run very straight -- and you need to put a lot of pressure on your idler and drive sprocket. Use Panda Plastics (ex-RHPS) plastic tracks instead if you must. Hope this helps