Anytime you start out with a new combo rocker arm geometry has to be set, no matter what length you come up with.
Mine are about .250 longer than stock.
It's a little more envolved than that cheap plastic checking pushrod you got, it's best left to a competent machine shop.
Heres a 'MUST' read on the subject.
http://www.compcams.com/information/Products/Pushrods/