Water channelling or "how to avoid ballooning"?

[Moonflower]

Does anyone have any suggestions on how to prevent ballooning in the fluke? I've made a pair of neoprene tails and I'm not sure what the best way to go about fixing the problem is. Should I just make the tips of the flukes open with little holes, or do I need to go back in and somehow add PVC, but what will that do to the overall shape?

[green52]

I would think adding small holes in the tips of the fluke would work. Where is the water coming in, through the waist band?

[Maple]

I've always thought little holes, say at the tip of the fluke, would work out quite well. It's either that or gluing the neoprene fluke pieces together, but then you wouldn't be able to take the monofin out.