New Trans and Mounts, unusual vibes?

[Tedzbug]

I just finished installing my KCR super street and homemade kafer style brace. HD trans mount with german rubber mounts, mid mount with urethane pads under horns.

It feels nice and smooth while driving and shifting, But when i am sitting at a light and put it in neutral i have a minor rumble/vibration. If i push in the clutch a little it goes away.

Is this just vibration transfer while it is free spinning or is there more.......?