Is the YHM forend rail on the same plane as a mil-spec flattop upper receiver?
Any feedback of pics would be appreciated. Thanks!

I had a rifle-length two-piece YHM on a Bushmaster A3.  The rails did sit a tad lower than the rail on the receiver.  

Can you define "tad"?

Well.  I never measured it.   I was just trying to let you know that they were not the same plane.  

Gotcha...
But like 1/4", 1/8" that range or more like the 1" or 4 feet?

Quoted: Is the YHM forend rail on the same plane as a mil-spec flattop upper receiver? Any feedback of pics would be appreciated. Thanks!

I don't want to remove my current BUIS because it's zeroed. (not the rail or scope displayed in this pic) To answer your question, it appears to be.  If it isn't it's very very close. Keep in mind there will be some movement of the handguards eventually as things wear. (mine are very tight).  My Tango down front grip fits perfectly, which means they fixed the milspec rail dimension problem.  My YHM FFHG wouldn't accomodate this grip.

I like this rail system and plan on getting the mid length ones for my most recent build.

I mounted a YHM 2 piece carbine length rail to my LMT A3 upper for "test fit" purposes.  The fit was very snug and the rails certainly did seem to be at the same height.  I got the sense that it wasn't truly aligned, but I couldn't say for sure.  

Then I removed them and gave them to a friend who is perfectly happy with the YHM.  Me, I just put my Knights RAS back on my rifle.