Why do you want a solid rotor. Had them on my 2005 Road King. Had to switch them out to a floating rotor. The OEM made a blood curdling squel, that would stop traffic. Harley hid from the problem, did the replacement on my dime. It was a common complaint, Happy after. Sometimes They get it wrong and you have to go another route.
I also had an '05 Road King that squealed. Funny thing, HD put the rotors on backwards. Swap them to the opposite sides and the squeal went away. I know it just sounds crazy, but it really did work.
@swakop_toe - Go for it. You're not new to riding. You're smart enough to check the rotors after rides and see what's going on and if an issue occurs, you'll be aware of it before it goes critical. A good machine shop would be able to trim the rotor down to 5mm w/o too much issue, it would just add to the cost. I have run 5mm rotors on an application calling for 4.5mm w/o any issues. 6mm may or may not be an issue with brand new pads, but I suspect no issue simply because the pads will open much farther than 6mm!
Give it a go and take pictures for us to see, then post your real world results. Saving R9400 is huge! That's $650 USD for those not familiar with rand exchange rates. (I do business with a RSA company) It would cost me $340 USD (R4,900), to buy OEM rotors with all new screws here, shipped to my home. I could ship a set to you for another $100 (R1,500). R10,800 is obscene.
A full set of aftermarket Chinese rotors can be had for $200 USD. That's all 3 rotors, front and rear.
FWIW, I have had good results with Braking brand of rotors, (Italian), and even some of the China stuff sold on ebay. As a retired machinist, metallurgy plays a part in brake rotors. Still, I would not expect critical failure with alternate materials. You're not doing destructive testing to failure.