My personal experience with the quick release wheel couplers is that the haxagonal type are sloppy and the steering wheel feels loose. I have this type and hate it.
I have seen several of the splined quick release and they fit very nicely, with little to no play, a huge difference, I would use this style if i built another one.
Also another thing i would do if you can, is mount the orbital down by the bottom of the radiator in a more oem steeringbox type location, and build a steering column to get to the box. This will shorten and clean up all your plumbing aswell as keep it away from heat from the engine and headers. It will also prevent air bubbles from getting trapped in your orbital when it's mounted as high or higher than your reservoir up at the dash.