So if the Burton strap doesn't fit, maybe contact Rome ask for a set of this season's 390 toe straps, which are open in the center and can be capped properly.
It looks like the 2011 390 has a flat strap designed to wear over the toe, which unfortunately has the compressing effect on the soft Vans toe box.
I guess asking for new straps cannot hurt. But FWIW the 11/12 390 toe straps work perfectly with my Vans boots - in fact they are just as good as the Burton ones in my experience. The Rome straps look flat but they actually stretch and conform to the boot really well.