I too had a problem with that POS stock tensioner. I don't like drilling into the cross arm as I would think it would weaken it and these bikes are not meant for this kind of abuse. I found this thread on a pretty good idea for a tensioner.

Spring Return Chain Tensioner

that looks like a VERY good idea and design. very little required to make it work.

I was engaging my engine and the tensioner went into the back wheel. 3 broken spokes later and a severely bent wheel I came to a stop. thank god I was only going a few mph. I will be taking the advice of the above thread and get myself this tensioner. I already have the 41 chain.