Other thing I like on the Combiplan is the fact that allows you to process glass plates by inverting the plastic hangers. I have a few boxes of expired Ilford plates I wanted to try, I also want to do my own dry plates one day and the tank seems perfect to process...
I do think the lid is a bit flimsy. I can never get it to fit good enough, so more often than not I'm ending up with developer and fixer all over the place...
Put the lid on the tank starting from one side, let's say left and close the lid towards the right by pressing about 2 inches at time, in that way you expel most of the air which is inside the tank making the lid stay tight.
I always do that and works perfectly for me...