So on a lark I bought a Spikes 9mm lower that takes the Glock mags and has the LRBHO. I was looking at the Fox Mike uppers, but there is a disclaimer on their website that they won't work with Spikes lowers. And the Spikes uppers are like double, if not triple than other 9mm uppers. Are there are other brand of uppers that are compatible with Spikes LRBHO lowers?