Very well done T-cut, it is the first time the fule system mystery has made any real sense to me.
A couple of questions....
I don't think the ITP pump type would generate anything like 52PSI, so why a pressure regulator there and are you suggesting that the regulator is actually in the tank? If it is indeed there, between ITP and UBP - why there, surely it would have been more sensible to have a regulator after the UBP?
The T, where the HP return flow goes back to the tank - I don't a simple T piece would work to share the flow between the two venturi pumps would it, without some extra help to force it to share the flow?
When that ITP does fail, might a second UBP in the line from the tank, make up for the failed ITP? The UBP is perfectly capable of self priming I found, from bench testing one.
OK four questions
Must admit I had not thought of venturi pumps to pump fuel from one side of the tank to the other. So I suppose due to the venturi pumps needing pressure to work, that the return system and cooler must be under some pressure?