1/4" return on sending unit

So I'm setting up my return style electric pump fuel system with a stock 73 dart tank. Have all 3/8 hard line (and -6an braided line), summit electric pump for carb mounted in front of the right leaf spring, Holley bypass style regulator set up after the 750 holley carb, and a spectra 3/8" sending unit with 1/4" return.
http://m.autozone.com/fuel-delivery...ding-unit/dodge/dart/796728_70445_0?location=

The issue I'm having is the 1/4" return port at the sending unit is causing a bottleneck making minimum pressure 8.5psi at the carb, and the carbs not liking it. Have tested dumping my 3/8 return line into a bucket and the pressure is a good 4psi which I can adjust up from there at the regulator. I'm aiming for about 6psi.

The question is has anyone else had this issue? Any better sending units out there? Because all I've seen are identical parts with different brand names.
I'm tempted to drill out the 1/4 return line and weld/braze in a 3/8 steel line that actually runs to the bottom of the tank, but am not sure how to prevent the level sensor plastic seal from melting... Another option that I'd rather not go with is drill out my tank for a -6an bulkhead fitting, and hope it seals.
Any tips would be appreciated!