About the only thing that will cause the gaskets to blow out like that would be either a bent flange on the exhaust pipe where it bolts to the engine or the flange is not laying fat on the engine. I had to bend my exhaust pipe a bit to get a good angle on it so it would fit flat on the engine and clear the bike frame. Try bolting the pipe to the engine using some extra washers. Run the nuts up finger tight and then take a look at how the flange contacts the engine. If it doesn't lay flat with no gaps all around it's edges the gasket shouldn't blow. If there are any gaps you'll need to straighten the flange and/or bend the pipe a bit. Also when bolting the pipe to the engine make sure you alternately snug up the two nuts, don't get one much tighter than the other as you tighten them. Pulling them up evenly is important to get a decent seal.
Goldwing 1500, Silverwing 600, Schwinn 49