Hi Converse, I'm pretty sure that plastic moulding at the bottom of the tank is to take up slack of the fuel line, nothing more. I recall seeing something like that on some more modern Victa tanks. As for your catcher, things must be different down your way, I have found plenty of those catchers in undamaged condition (I only found one recently and didn't even bother taking it -I have plenty of spare ones but now wish I grabbed it anyway.) I like that your one has the twin grip label so intact, only one of mine still has it. That's another sign of how little use it's had. I found a thumb latch in pristine shape in a mower shop dumpster years ago but with the latch mechanism missing, so stored it for a few years only to discover it fitted my Victa Twin!! I got the latch off my old cracked green VC Mustang catcher and it fitted straight on.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!