ROMAN LEGIONARY GLADIUS TRAINING VIDEO

[Quintus Claudius Scaevola]

You're locking up the shield and not using it to the fullest by having the right leg forward as you mentioned, however as legionnaires were typically right-handed, you would increase the range of a thrust or cut. When a martial artist punches, rear punches or crosses aren't typically very powerful unless you advance at the same time, transitioning to an increase in range and power from the now lead hand/leg. In a stationary or defensive position, a thrust or cut with the rear arm tucked back loses both range and power. Thus with your right leg forward you have a bit more advantage in a strike. Whether it's worth it compared to bracing you shield, however, I'm not so certain about. You can always give it a try on the pell and see if you notice and difference.

-Quintus Claudius Britannicus