Utilizing Plastic Measuring Bands

Based on the advice here, I want to pick up a metal cage. The sizing ring kit from MM seems like a solid buy. It fits me in the 1 7/8” A size and feels comfortable enough. My main worry is keeping it on for three full days without slipping out due to cold-induced turtling; being naturally high and tight makes this harder. Since my KH keeps our bedroom at a chilly 68°F, avoiding that temperature drop can be tricky. For those who have sized before: should I stick with the A ring, or is it safe to rely on my sizing ring experience plus my current CB3000 setup when ordering either a Jailbird or Contender?