The early PS and RPB M-11s share the same single loop stock as the later SWD M-11A1 guns.
If I was looking for a stock to use for shooting the OEM upper, I'd opt for the SWD M-11/9 double loop stock. The single loop tends to slip off your shoulder while firing. The M-11/9 double loop stock is a huge improvement and it still looks correct... Mostly. If you don't care about it being "correct", I'd opt for a Practical Solutions Mini Uzi side folder if you desire the minimalistic look. It's a solid stock that folds and still allows use of your factory sights.