@P5music: Please note that the loop-mounting of extension will always use '/tmp/tcloop'. To make it a bit more clear:
(1) Let me start with the case of the "cloud" mode (which is not what you are aiming for, but to explain things step-by-step I'll begin here): Extension files (e.g. EXT.tcz, plus their respective .dep and .md5.txt files) will be saved to '/tmp/tce/optional'. The "installation" happens via loop-mounting using mount points under '/tmp/tcloop'. Please note that '/opt/.tce_dir' contains an entry of '/tmp/tce'.
(2) When using persistence (which is what you are aiming for) the system should "automagically" identify your "tce" directory on your pendrive and use that instead of '/tmp/tce'. For argument sake I will assume your partition is '/dev/sda1'. If the detection works properly, the entry in '/opt/.tce_dir' should have changed to '/mnt/sda1/tce'. The extension files should be saved under '/mnt/sda1/tce/optional', but the mount points for the loop-mounting are still under '/tmp/tcloop'.
In no scenario I'm aware of should there be any EXT.tcz files under '/tmp/tcloop'.