You're right that a lower pitch should slow it down somewhat at idle, but there won't be a huge difference. Keep your high end needle rich if you try the 11x4; I think it's going to rev the .46 pretty hard. 11x5 might be better.

If the landings are giving you a lot of trouble and you're in the mood to experiment, you could take an idea from another ARF trainer (can anybody post the name?) which uses permanently deployed airbrake type things near the trailing edge root. Just get an experienced flyer to try it out the first time..