The gas checks are crimped on when they pass through the sizer. They aint coming off.No problem then with lube being under the gas check and having it fall off? I'm just wondering because I saw a nice mold I want but it is a GC mold.
Worrying about them falling off after sizing is like worrying about the wheels coming off your car after the lug nuts have been properly torqued.
I've never had a problem with the bullets made this way. I've loaded 30 cal cast bullets with gas checks in 30 carbine, 30-30, and .308 and all shoot fine with no ill effect. The gas check stays on snug from breech to backstop.
If you don't want to use this method then feel free to spend the money on a lubesizer. I've never owned one and never plan to. Tumble lubing and Lee Size dies for me.