Hey guys I found a bit of info on k cup filter use.
"
I start with a medium grind. You don't want it too coarse (like in French Press range) or too powdery. Somewhere in the middle is pretty good. Mine leans more towards coarse than fine. It helps (as it does with any coffee brewing method) to have a good grinder that gives a fairly consistent grind size, but you should be OK even if you have a cheap blade grinder, you just won't get optimal results.
The secret is to pack the coffee down a little bit (not too much) by tapping the filter on the counter, but also leave space at the top of the filter. If you don't pack it down at all, the water will flow right through and you'll end up with a weak cup. If you pack it down but pack it too full, you'll have the pressure problem. The Keurig will think it needs to be descaled, and it won't brew a full cup because of the pressure.
So I've found that filling it about to the lip, and then tapping it on the counter a couple of times gives me a good result. I end up with about an eighth of an inch of actual visible mesh in the filter above the coffee grounds, which gives it a little room to spread out so I don't have the pressure problem, but keeps it compacted enough that it extracts fairly well.
"
Hope this helps.