I used the .215" tall x .125" wide Dawson ramped serrated black sight. This was an option when ordering the LowPro mount from the CHPWS website. The also have an option with a fiber optic front sight. It was my understanding that the stock front sight was a bit too short to co-witness. I did not try it though. I wanted to use the black front sight as opposed to a fiber optic front sight anyway.What dimensions did you choose to install?
Could you co-witness with the stock sights before replacement?
You can order the front sight from the Dawson website and save few dollars actually.