I have an isonic (same straps), but the hole locations may be different than the Futura. However, I have 45/46 feet (US - 12) and the staps after 8 outings and several re-adjustments are still too tight with winter booties. They are OK but hopefully they will continue to stretch.
I haven't tried the crow bar except with my hand and arm.
The problem with the isonic is that the straps are so far outboard, so I have to rotate my feet in the straps to keep them from catching in the water.