I use an armotech wg-65 elite, with a custom vest from cops911
Anytime you carry two guns on your back, weight is involved. Grow stronger.
The strengths involve stability, and quality. The fabric is awesome - some of the most durable material ever used. Also, you pull two huge robocop pistols from your back, and almost anyone will s**t themselves.
I used this bad boy for a while, then simply emailed them a custom vest I wanted and they made me whatever I wanted. I now roll with 4 pistols, 2 in front, 2 in back. I love this holster.
Sign up with cops911 for free, and they give you 10% off EVERY order. So, even if you think that the prices are a little, steep, GET THE 10% OFF! You wont regret it - I 've met the guy who runs it - and shipping is fast, and the service is friendly.