I use water wings! You know, those little blow up floaties they put on infants arms. Ha Ha   couldn't resist   (sorry)

Competition (aka not coast-guard approved vests) are not really known for their floating prowess. Some do better than others, but I can't think of many that couldn't sink if you tried. The ones that do float well missed CG certification by a inches not miles. Where you are floating sounds about like what I see from other skiers and myself. Do pay attention that you are not exhaling on your downward bob, that's like pumping your legs on a swing.

check the posts on the Eagle vests. They can make you a vest with all the flotation you need. They offer different mil thicknesses of foam. Costs and extra $50 to have something custom.
Check out my vest, check Tadd's add-on this week.
They're made out of wet suit material, so they're flexible. They pull around you real tight like a wet-suit, so see if you can try on one before ordering a custom.