Mike - It's very hit-or-miss as to whether a primary radar will pick up a glider or not, regardless of its distance fronm the radar head or how new the radar is. There are just so many variables involved. Here are a few; wx, time of day, age of glider (metal bits vs composite), raw data or plot-extracted, supression used, relative attitude of glider, track & speed of glider and so on and so on. It's often just "a feeling in the water" when you call it.
Fournicator - However lightly you use the term, remember that especially in mil aviation "Air Tragic" are a part of your team & you should not be avoiding them. You've probably heard of CRM? When we do a "check gear" call it's not for our benefit! I suggest you spend more time with them rather than less to find out their abilities & limitations.
Dimension - it's not the practice of a mil emergency procedure in mil airspace. It's that you have to consider the WHOLE picture which includes ATC equipment serviceability. Personally speaking, if you want to stick your nose into the clouds outide CAS & in high-energy manoevres when my radar's less than perfect, that's entirely up to you. It's your nose!
ap
edited to add -
Remember, on SSR only a 747 could fly across the top of the ATZ at 2001' & not talking to the unit quite legally & the radar would not pick it up it he's not transponding. Not a 747 admittedly, but mulit-engine jet airliners HAVE crossed my ATZ at 2000 not talking to me. OK, so the ones I've seen have been transponding but have I seen all of them ?Your call!