Couple things I noticed:
Enlarging the valve stem hole in the wheel won't do much to protect the tube if you spin the tire on the wheel. If it really spins (very unlikely) it will tear the valve stem out anyway.
What will happen is crud (sand, small stones, water and junk) will get into the hole and inside where it will grind up your tube and may cause a flat. This will happen off road riding. I would round up the hole (neatly) and find a rubber grommet to fit. Keep the crap (and WATER) out of there! Water inside will rust and corrode spoke nipples over time and potentially ruin the wheel.
I also notice your spokes nipples and wheel look a bit corroded. (from Salt back East?) Watch for cracks!
I was curious why you were grinding down the Chain pins? (Rivets) If you have the Motion Pro chain tool then you can just push the pins out in order to cut the chain. No grinding needed. A chain tool is faster and easier.
I forgot to mention one thing I noticed on your bike regards overheating.
Front Fender: I notice your fender is cut. There is a reason Suzuki (and off road bikes) have the back part of the fender there. Mud splatter.
In mud riding, without the back part of the fender, you can get a lot of mud build up on the engine and Oil Cooler. Eventually you've built up a nice insulating barrier and air will no longer cool the bike efficiently. So if you want to run the cut fender then try to keep the motor clean of mud/crud build up. Some mud is like Pottery and gets cooked on there!