The injection molded cone is not only heavier, but it's almost 1/4" shorter than the modern blow molded version.

I built my Omega Cineroc clone straight from the Omega plans and everything worked out just fine. If you ever do fly a heavy payload with it, be sure to use a long rod and fly on a calm day. It tips off easily, especially if you forget and put a poopy clay D12-0 in there and the nozzle erodes enough to give it vectored thrust.