I tried somthing similar to that running two into one.
I had trouble with the over flows running uneven one or the other
would gurgle off and on.
But my set up was differant for the way my sump was set up, I had to run all my plumbing to one side then down into sump.
Being as yours is centerd you may not have the same problem I had.
The only thing I can think that may be a problem is the pipe size,
2-1" pipes into 1-1.5" may cause a bit of restriction,
But that probably depends on the size of the return pump, and how much GPH you're overflows are rated for.
Be sure you support that plumbing realy well, that is a bit of weight hanging from the bulkheads, even more when you get water flowing through it.