Realizing your concern on excessive pedal travel, going to a larger piston on MC will certainly decrease it, however at the expense of lessened clamping pressure on front disc,,,which you indicate is not sufficient with your manual brakes to lock front wheels.

Are you certain that your new MC was properly bench bled, that brake lines are truly purged of all air,,,including bleeding at both valves on each caliper,,,that if using dot 5 brake fluid that it did not get shaken up before use which will cause millions of microscopic bubbles, that there is no flex in calipers when pedal is depressed hard.

Are you bleeding the old fashioned 2 person method,,,I have an expensive Mity vac air compressor vacuum system,,let's just say I have become a confirmed skeptic. Oft times the old ways are better.


My suspicion is that a 15/16th MC would be the way to for the front disc brake pressure you require to lock up,,,,your long pedal travel is a problem that lies elsewhere.

Just throwing some thoughts out there.