Note, if matte gets scratched, it's done. With gloss, you can still do some minor polishing to get scratches out. I was going to do matte forged carbon and was advised against it from the company because of that reason.
I've had zero quality issues with my R400. I also had it on my FK8 and had no concerns. I personally wanted a burnt triple-tip, as well as one that retained the valve. To me, the R400 had the sound I was looking for. I like a deep throaty exhaust. I wasn't concerned about drone, as the car is...
Location and timing can be a major factor. In Upstate NY they are not heavily sought after. I got mine for $1200 under MSRP and negotiated them to throw in the high wall floor mats.
Haven't done the install yet. I rarely drive the car, so it hasn't been a priority. The OEM on the FL5 are plastic. Not worth taking the chance with an aftermarket sway.
You might want to specify how far you are willing to travel. You could also find one at MSRP and ship it. In the end it would still be cheaper than dealing with huge markups.
I really don't think it's too late. I would circle back to him and say you didn't realize how much of a pain it was going to be and that you need the dealer to do the work. Get a quote from the dealer and bring it to him.