rear oil seal silicone needed?

Question: I forgot the rear oil seal on my GL1200, 1985, and put the engine back in the bike. (Stupid mistake.) However, I put it in by removing the clutch slave cover and shaft and just pressed it in there by hand until it was level with the surrounding surface. I put the shaft back in and cover back on.

My question(s): will that hold? What holds that seal in there? Should I put a little silicon on it to help it stay in?

Thanks.