The rear adjustment was most convenient when everything wasn't drilled just so.. Today that is for the most part irrelavent. It does have another positive side though. Scopes, especially the higher powered ones and higher powered variables most of all, function best near the center of their lens systems. While the difference is small it is a difference. By centering the scope's internal system and using the mounts adjustment to get everything close, the scopes internal adjustment only is used to fine tune the zero(windage anyway) and the image stays closer to the optical center of the lense'. As for as them being strong enough, I suppose anything can fail.. I've only had 1 set of Redfield mounts fail and that was simple scope slippage. Cured the slippage and replaced the damaged adjustment screws and the weapon was happy again. The adjustment screws were over tightened in an attempt to stop the scope from moving. It was slipping in the rings so the adjustment screws were damaged without reason..I lube the front dovetail with a high pressure lube at assembly time and work it a bit to allow the adjustment screws to easily rotate the scope left-right to center things. Actually this type mount almost cannot maintain any stress on a scope tube as the front ring will turn to face the rear ring. The only possible stress then being in an up-down direction. As to clearance there is precious little difference between the 1 piece and the 2 piece. all access is from the ejection port which is on the right and the 1 piece bases are clearanced. The real advantage of the 2 piece mount is the ability to buy bases that will reverse. This can allow more latitude as to the positioning of the scope front to back,. With some of todays short coupled scopes eye relief and scope position can become a problem. It can be solved with offset rings but these while usually OK are weaker. Much better to turn the bases around to change the mounting position of the scope..