I'm sure this works fine for you, but I would in general
not recommend that people do work on their spare time. The reason to do that is, as you point out, that you get to take all the risk, and your company gets all the profit. That's not, generally, a healthy employment relationship and as an employer, I would be pissed if I found out someone did that.
Just carve out an hour every day from your salaried time to chip away at these projects. Nobody will ever know unless you tell them.
