These are made for 3 bladed props - won't work with two blades. I used an FSK 9x7 turning normally in the back, and a GWS 3-bladed reverse prop at the front. They weigh around 7g (latest revisions are 4g) and I just superglue them right to the prop - fast and easy, and not had a problem with that method. I printed at 50mm/s sec, eBay PLA on a Printrbot simple metal. To post process it, I sanded with 80 then 180, then rubbed just a bit of oil in the surface to get a nice consistent matt finish.