Do you think this could be tested?
I have the amps and sutiable speakers, a UMK1, & REW, but I'm not prepared to move the speakers, would a nearfiled in room measurment show anything?
Yes, REW measurement should show phase correctly. Try making a sweep measurement from app 70cm away from the speaker, use "Estimate IR delay" and shift IR for as much as REW suggests and then apply FDW of 5 cycles. With a little luck wou will get a clean phase response graph.