Gentlemen if happen to come across a Toro LX427 with a deck belt issue just be aware that the Toro belt 112-5800 is a MTD 954-04045 which both a spec'd at 1/2 x 109" can be replaced with a shorter 1/2 x 108 belt. It is kinda pushing the limit as I would have to gone with one around 108-1/2 but I wasn't able to find a clutching belt in that size.
The problem here was sluggish deck engage due to the belt slippage especially at the lowest deck setting. Also the engagement idler arm showed signs of hitting the other idler pulley. Actually has a groove cut into it. The 108 is close to being too short at max deck height but didn't drag on the engine pulley when disengaged. Besides this customer need all the help he can get on the deck as it is used in full mulching mode.
Basically like another MTD deck that I work on here that specs a 103/1/4 belt where it needs 102" at times due to same slippage.