What's a reasonable bonus for my GC

[Griffin Malcolm]

Approaching the end of my first BRRRR (rehab to be done in 2 weeks) and I'd like to reward my contractor with a cash bonus; I'm wondering what an appropriate amount of money is to give him. Percent of the rehab amount? Flat bonus? Here's some more context:

Rehab cost about 30k. We involved his guys for paint, siding, carpentry, flooring, sheetrock, electrical, and demo/trash haul. I really didn't have to lift a finger. My contractor made all the calls, got everyone in there very quickly, and has stayed right on budget. He has even come to my personal house to pick up money and some things I ordered from Amazon to be installed in the property, and fronted some of his own money to keep things moving while I wait for the draw from my lender to clear. He really has been a rockstar and is locked in to keep doing more properties with me. I really couldn't be happier, so as such, I want to give him some money to show my appreciation. 

I was thinking I'd give him an extra $1000 cash when we're all refinanced. Is that too much / not enough? I truly have no idea. Advice would be appreciated, thanks!