By replacing the frizzen on the Investarms lock with a Seiler small rifle frizzen I was able to get the flint to hit on the upper third of the striker plate instead of the bottom 1/4 of the Investarms frizzen. Not much of a change but better geometry for the flint which resulted in a much better spark. It made a big difference with my rifle.
It looks like the L+R RPL05 lock is a close drop in which would of been the way I would of gone if I knew about back when I was having trouble. The L+R locks are also nicer looking IMHO. Might splurge for one if I can save up the cash.
Real pretty rock lock you have there rfd.