OSTHEER IS DONE WHEN IT'S DONE!
I'm not sure what you mean by getting 4 shreks on a squad. You can still only get a maximum of 2 because PG squads (number of men is irrelevant) have 5 weapon slots. They can however, attain 4-5 bazookas or BARs since they only take up 1 weapon slot each.
I just found out that PE shreks that are dropped turn into Wehr shreks on the ground. PE shreks take up 4 weapon slots (PGs have 5) while WM shreks take up only 2. Therefore, a PE squad can pick up 2 of his dropped shreks but can only build 1 on himself.
There was a screen shot in one of the posts showing a VG squad with 4 Bazookas and a one man Amis Bazooka in ! retreat. .