I love the cosmetics! I think it would be cool if there was yellow on the Batman side but it's cool none the less. I would highly suggest replacing the plunger head as stated above.
I only advantage that I see with a homemade wye is that you can customize the angle. If you have a mellower angle you can use longer darts with the system and darts should load smoother. Try a 40 or 35 degree angle next time. Nice job.l
If you don't have pipe cutters or don't want to risk using boiling water, try roatating the plunger assembly over a lit candle. But be careful, it is easy to melt the plastic.
For a 17/32" angel breech you simply down size each piece of brass. Coop772 on youtube has a very nice, in-depth video write-up on how to make a 17/32" angel breach. Here's the link.