I just installed a bigger clam cleat for the mainsheet, rated max line 1/2". Amusingly, It is still too small for my current 7/16th sheet and so, yeah, "not very secure."
I only use it when reefing and it is an admirably simple and cheap hunk of plastic. But a cam cleat is probably a better choice for the application.
I only use it when reefing and it is an admirably simple and cheap hunk of plastic. But a cam cleat is probably a better choice for the application.