Typically you cannot fold the stock with an optic mounted to the side optic plate, or with a side mount intended for picatinny or weaver optics. The triangle and poly folders are designed to latch over the side rail when no optic is mounted, but when an optic is mounted there is not enough clearance in the stock body to latch properly.
ZeniCo makes a side folder that when combined with the
B13 side mount allows the stock to fold and lock with the B13 on the side rail. Using the PT-1 stock and the B13 you could mount a decent optic to the B13 and still fold the stock.
You can use the
B33 topcover or other top cover systems like
TWS for example.
There is always the classic
Ultimak gas tube rail if you want to mount a good red dot over the gas tube.
I don't have direct experience but
Attero Arms does a rear sight block mount that seems to get reasonable reviews
For reference the SLR104 has the 4.5mm hinge folder. Modern Russian gear is 5.5mm but the ZenitCo stock has an adapter that allows it to swap between 4.5 and 5.5mm hinges
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