This is a small modification and I haven't seen it on before. My 416H belt flopped around so bad that it hit the side cover, after putting on a new belt it didn't improve much, so I added a flat idler. My 520H belt was missing about a 1" chunk, so after installing a new belt, it had the same issue. The idler is 3 1/4" and is from TSC (3" to 3 1/2" would fit fine). The tension idler on the left raised up slightly but wasn't a problem.
There is already a hole in the hoodstand, I used a 1/4" bolt, but the hole is the right size to tap 5/16" threads if you wanted to use a larger bolt. With a couple of washers a spacer it was installed. I was tightening the steering and had this apart already. I got similar results to Duke's post on the steering play. It's not hard to adjust, but takes a lot of time.
Just my
Craig