After some research into adhesive types, I came to the conclusion that I really wanted silicone adhesive, for it's flexibility and low adhesion.(so I could remove it later) I could get 100% silicone caulk, but it uses the same curing method with moisture from the air, so wouldn't work. Purchasing a two part silicone would work, but it's expensive, and I didn't really have time for an order. I remembered that cosplayers have been using silicone caulking without this problem.
There are a couple methods for getting silicone caulk to cure without air(usually this is because it is a thick layer such as making a mold. The cornstarch method is probably most popular, but it seemed like the stickiness was lost with this. Likewise, the water and dish soap method seemed to be effectively creating a barrier between the silicone and the surface preventing adhesion. While this is perfect for making a mold, it is not helpful for using it as an adhesive. Some deeper digging resulted in the answer though, glycerin.
Mixed with 3-4 drops glycerin to 1oz 100% silicone caulk, and the result would cure quickly without exposure to air/humidity. Glycerin is available in many drug stores, usually in the beauty section sold as a skin treatment. Ideally find the bottle of liquid, and not the suppository which is probably harder to use and more expensive. For example, http://www.cvs.com/shop/beauty/skin-care/body/cvs-usp-pure-glycerin-6-oz-prodid-1015638 For the caulk, I used white because it was on clearance at the hardware store, but most people use clear.
Testing this, it did work great. I used a solo cup with it's convenient graduated markings to measure out 4oz, and put in 15 drops of glycerin. I used a plastic knife to mix it. The smell is overpoweringly terrible, so be sure to do this outside. I mixed for a couple minutes, not sure how to know if it was enough before applying it. I would recommend adding a small amount of acrylic paint(the cheap $2 paint bottles at craft stores) along with the glycerin. This way you can use the color to see when it is evenly mixed.
Using the knife to spread it on the monofin, I re-attached the plastic
I used some more to spread across the edge transition, and a scrap "credit card" the smooth that section out. I left it to cure for a bit, and repeated the process for the other side, but this time I applied it to the plastic as well, to glue both sides together.
This time, it cured perfectly. I didn't pull too hard to test because I knew the adhesion level was low, and I didn't want to pull it off. To ensure it had cured, I left the extra from each batch I mixed pushed up in a ball, which ended up about 2" diameter. Despite the thickness, it completely cured after a day, which ensured that what I put on the fin was also cured.