Those look great!
As far as drilling into the real GRAFLEX... since you've already glued your t-tracks onto it, you might as well. You really aren't hurting it.
Being in the conservative camp when it comes to vintage parts, I'd recommend not drilling a vintage bottom. These things are getting so valuable nowadays, that I can't imagine what it will be like in another 10-20 years. I remember when Ebay first started and you could find excellent condition Graflex 3-cells on there for $100-$130. Nowadays, a vintage bottom alone can go for over $300--even more if it has the ESB wampa cave "NEW YORK" roll mark.
You can get a replica bottom from TGS or Roman for $55. Why not get one of those and drill that and keep the vintage one intact to preserve its value?
They're worth about $20 as a camera flash. All the value comes from Star Wars, as a lightsaber. So anyone else who wants it the future will pay top dollar if it's drilled properly. That said, if it's only ever going to sit on a shelf (perfectly great idea), the bottom can obviously be attached in a non-permanent way with some 3M VHB tape, etc.