yes the lockblocks will work fine, on rougher trails you will get some bouncing..
I like this mount for larger lights and more secure feel, you will not have a bouncing issue.. They work with 26.0 and 31.8 bars as well
http://cgi.ebay.com/NEW-360-Bike-Bic...item5ad4d8fed7
You will need a small piece of rubber to put next to the light for a super snug fit..