Sorry to hear of your sizing issues. Without direct supervision during the measuring process refinement of the fit may be required.
Most uncut guys retract the foreskin to seat the silicone ring directly behind the glans, however, there are some who prefer the leave the foreskin covering the glans with good results as well.
There are some many variables with component combination combinations, anatomical configurations and personal preferences that individual experimentation is required to find out what works best for you.
The Retainer Band is of relatively “loose” elasticity so you will not have any problems with contraction. You can control the tension by positioning it at different layers whether it be directly on the Innerwear or for more tension on t top of the spandex sleeves.
all the best with your resize!