Upper reciever help for a dummy

[Hallboss]

I have three "A3 Flat top" uppers. All three of them the rail is higher than the 12 o'clock rail on the forearm and I hate them. Stupid me I assumed a flat top was a flat top and evidently they are not.

I want the upper that the rail is the same height as the forearm. What can I do to ensure when I buy my fourth upper, it's the right one.

Thanks for the help.

[Failure2Stop]

What railed HGs are you using?

[Hallboss]

YHM, but the big reason is I want to use either a POF or a bushmaster with the extended rail.