Welcome to the Forum.
2011 NEC 424.9 basically says you have to install the baseboard heaters in an approved manner. You know, follow the instructions included with the heater.
For fun, I just read a copy of a Cadet baseboard heater installation sheet. One thing they say for their baseboard is, if we don't show it hooked up like you are doing, you shouldn't do it. And another thing they say is they specify a clearance of 12 inches above the heater to anything else.
I recommend you look up the instructions for the units you are asking about.