The choice of plastic at the top of a metal magazine seems odd. The precautions you highlight all make good sense, think I'll start to load with fewer bbs as I want to keep the spring as is so that the lockback operates as it should. Fewer bbs might help in other pistols where double feeds occasionally occur.
I guess they would not sell as many if they were promoted as 7 or 8 shot, most users want convenience (fewer reloads); maybe they should have used an all metal magazine.