If you must use a single trigger and that TG, I would split the difference and place the front post of the trigger guard a hair past center of the tumbler axle (as Tom Currie said) and put the step back even with the comb, cheating the TG rear return forward a little so that it seems to grow from the step. As long as the rear strap/post of the trigger guard is starting to curve when it emerges from the step or shortly thereafter, it should be OK, for me at least. It doesn't look right at all if the step is ahead of the comb, in my opinion, only.
I think the real answer is Mark Elliot's: go to double set trigger and larger bowed TG.