People have been doing it for decades. lol
Pioneers !
My first was putting a solid flat tappet on a hydraulic shaft as a poor teenager.
I guess it doesn't hurt to ask............ but I prefer the pioneer aspect in everything I do.
Call me crazy, but I don't think putting solid flat tappet lifters on a Hyd flat tappet cam, is the best way for someone like me to run a business. Especially with todays apparent lifter quality.
But if you want to do it on your own stuff, then go for your life.