1. Make a split cover. like a typical gearbox would be.
2. Make a slanted cover.
3. Make the cover come off the *front* not the top
4. Tie bolt that interfaces at an angle
5. Move the bottom "floor" plate up so you fillet weld around the underside rather than the topside
6. Use long through bolts rather than tapped holes. Or at least, through tap the "floor" rather than post drilled blind holes
7.