I chose this pull buoy because of the deep concaves

I chose this pull buoy because of the deep concaves, meaning that you dont have to squeeze your legs together to hold it in place and can just concentrate on working your arms. However there's 2 problems: 1) The edges are far too abrupt making it uncomfortable 2)Thers's too much volume and my legs are lifted too high out of the water (I'm thinking of taking a knife to it for both of these reasons).