I found with conicals the general rule of thumb is if they are flat based put a wonder wad under them. It creates a better gas seal and you get a better uniform load. If they are hollow or concave as you say, they would not need the wonderwad. Usually when they are hollow in the back, as the charge expells them up the barrel the back end of the conical will engage the rifling.

The hollow point ballets and conicals work real good on deer. If you hit bone you get a massive wound channel. I have shot almost every brand out there on the market. My Renegade with 1-48 twist shot all of them real well. As you state, to save money I began casting my own conicals from the LEE R.E.A.L. molds. I shoot a .54 caliber so I cast a 300 grain and a 380 grain flat based conical. I use a wonderwad. I get real good accuracy out of them and they will take a deer off their feet.

They make nice big holes too.....