Looking at finally getting a choke for my youth 870 20 gauge. Not a full build out yet, but an alternative to my 28" barreled SX3. I'm seeing chokes ranging from .550 at the tightest in the Tru Glo SSX to about .575 at the loosest which comes in a number of flavors. Wondering where some of you guys that run 20 gauge Remingtons have landed for choke diameter, especially out of the 21" barrel. Thanks for any help!