I had a JP Mkiii and had substantive contact between my gas tube and the handguard (Kreiger rifle gas, 6.5cm, .936 @ gb journal).
It pushed the tube down enough to cause interference between gas key and tube. This resulted in some strange POI issues as things heated up.
I replaced it with an SLR Ion 15.5" and never looked back. Plenty of vertical room for the gas tube. I also used an SLR adjustable block.