I had the same issues on my Trail. I HATED the chain tube noise and knew it was costing me something in effort. So, when I put on the adapter and the 26" rear wheel, I also got a 'power side' idler from Utah Cycles and installed it. Additionally, I cut down to chain tube on the return side to about 3" where it wanted to rub the frame under the seat. The result was a VERY quiet chain, and better transmission of power to the big rear wheel. Utah also sells a return side idler, to eliminate any chain tubes at all.

Tractor Tom in Okeechobee, FL