The diameter of the rear peep governs the brightness of the sight picture.... If you have a high contrast and good lighting, you can use a smaller peep.... If you're hunting, you may need nearly 1/8".... Some globes are adjustable for windage and elevation, that would be necessary for the "simple" version of my scope ring peep.... As you say, an adjustable ring would do the trick, all you have to do is find the correct height globe to go with it....Bob