RE: dave brown motor mount and saito150
I have never used the sheet metal screws supplied with Dave Brown engine mounts, because they don't seem secure to me. Since I have never actually tried it, I really don't know if they would be OK or not.
If I had used the sheet metal screws to mount my engine, I would check them pretty often for the first year or so. I recommend you check yours, and it might be helpful if you post your findings for the rest of us.