I have a solution to your problem.
Or buy a quality quad rail.
Ray is right on the money, BC is good stuff for the money.
One thing to keep in mind, you get what you pay for.
I can guarantee you that the rail from eBay is soft, probably not to true
picatinny specs and the anodizing probably is not much better than rattle can black or magic marker.
Probably much heavier too.
Spend your hard earned cash on the very best you can afford.
That way you are never disappointed.