I've lost one of my Tossberg's leg protectors, so I've modeled a similar one.

There are two variants:

• with indent for 16x20x3.5 felt pad — combined with felt pad height it will match the original protectors' height.
• without indent — you could attach felt of any size, but the height won't match the original protectors (you can print all four of them in that case).

I've tried it with PLA. Print standing up for better strength (original orientation).