Best head gaskets for jet boats? MLS or Graphite?

​​My Vortec 350 has slipping compression and has sprung a couple drippy coolant leaks around the head gaskets of the rear cylinders. Three years ago when the engine was fresh the compression was about 200 PSI per cylinder. Now it is 180-200 with one at only 150 PSI. I've had two previous engines blow out between the middle cylinders. The current gaskets are Felpro MLS. The first two engines that failed and were damaged beyond repair had graphite gaskets. The engine is a stock GM Vortec (Marine Power) with the stock "Ramjet" cam, it turns an "A" impeller at about 4,450 RPM's, about 325 hp. It is also raw water cooled and hooked up to an an American Turbone SD-309. I have never overheated this engine and always allow it to warm up before putting down the hammer. I run about 32 degrees total timing. The spark plugs look normal. There is no water pressure regulator. Is the unregulated pressure likely causing gasket blow-outs? I use this boat all year and winter in Massachusetts. This boat also sees extended full throttle runs of 45 minutes sometimes running up and down the Connecticut River. I'm getting tired of replacing / rebuilding engines every 3-5 years. I understand that MLS gaskets need more precise surfacing. I'd rather not pull the block out for special resurfacing if it looks level. Can MLS gaskets seal better with the old copper spray? Recommendations? Thanks.

Best head gaskets for jet boats? MLS or Graphite?