I plan on keeping a 2x10 drivetrain on a couple of bikes, and I've come across a sale on 10s cassettes. One of the cassettes is a Shimano HG-500 with 11-42t count. The front drive will be either 34-24 or 38-28. My rear derailleur is an XT RD-M781 SGS cage which specs out as max low sprocket of 36 and total capacity of 43t. If I were to put the 11-42 cassette on, the total capacity count is 41. I realize that Shimano is very conservative with their specs as far as maximum tooth counts, but six teeth over the max low sprocket spec may be a bit much.
Anyone care to chime in on any experiences with a similar set up? Or thoughts on the question, if I've exceeded the tooth count on the max low sprocket but not the total capacity of the rear derailleur, can I expect good shifting?
Notes: yes, I'd like the low ratio to defeat some steep berms that have thus far defeated me.
I typically match up a dedicated chain to a specific cassette, so the 11-42 would come with its own sized chain.