I've seen two Ryca cafe racers side by side, one with stock fork springs the other with Progressives, and the one with the Progressives was taller in the front. Has anyone else noticed this? Is it normal?

The Progressive springs ARE stiffer.  With lots of weight on your arms, wrists, and hands because of the clip-ons, when you hit railroad tracks and other bumpy stuff, you have to keep your mouth closed or you'll lose the fillings that just came loose.

I'm thinking of wearing a boxing mouth protector to keep the lower teeth from repeatedly slamming into the upper teeth.