In reply to stu maci: Not sure if it will help but I have the vassaks and I use them with a pair of Scarpa Freneys and once I replaced the linking bars with a curved set they fit perfectly. If the mantas and omegas have the same asymmetric footprint as the Freneys then the change in bar is a must but it will add to the overall cost.
In reply to neil45th:
Mantas are not as asymmetric as the freneys. I have freneys and I deliberately choose crampons that don't need the assym bar as I don't like how it makes the front points angle in so much. Sabretooths and Rambos are great on freneys and the front points point in the right direction.