What is being used to put on the engine hatch as mirror material? Polished SS sheeting, Acrylic Mirror Sheet, polished aluminum diamond plate? these are some of the ideas I had. Second question is what would be the best way to adhere it or fasten it to the engine hatch?

if using plastic use polycarbonate ,its heat rated,,regular is not and will warp..

Acrylic Plexiglass Mirror in the color of your choice. Ebay was the lowest price place I found them before. $40-50 for 2'X4' sheet i believe

If you want it to last, use polished stainless. Fuel and assorted chemicals will turn the acrylic cloudy......

I used stainless on my donzi and it came out great (the second time). On the first go around I laid the hatch upside down, put down some epoxy and then the stainless. I added weight to secure it until dry. Low and behold the curve was gone out of the hatch. Had to remove and reinstall in a bowed position to make the hatch match the deck. Also note the stainless adds some weight.

OK should I screw it on or glue it on?

Glue is a cleaner looking install, just have to get some really good adhesive that will not be affected by heat.

3m 5200 would do it. I haven't made up my mind on how to adhere it yet. Nice looking SS mushroom head hex drive screws might be good.

If anyone tried to send me a message my box is clear now.

I used 3m tape on both my cigarette boats for plexiglas mirror. I used a lot but it worked well. The surface was gel coat finished under the hatch for your info. Held 1/8" no problem. But I used quite a bit. Depends on your surface.... Good luck