Briding center channel speaker

Negative is the key word.

This is a wiring configuration you will not see in any wiring diagrams.

Each tweeter is getting an AC signal;  it alternates from neg to pos to neg to pos etc.  This is true of any speaker in an audio system.  When you look at the wiring as displayed here, you see that the left tweeter neg meets a 4 ohm load, and that the right tweeter pos meets a 4 ohm load.  What do the other two wires meet?

Right, a 4 ohm driver and 6 ohm driver that are parallel-connected, which is a 2.4 ohm load.  https://www.the12volt.com/caraudio/boxcalcs.asp

How do you suppose that's going to sound like?  For basics, the crossover is designed to match the given tweeter to the mid, and it's also designed to separate frequencies according to a given impedance.  That impedance is designed for 4 ohms.  Look at https://www.the12volt.com/caraudio/cross.asp, specifically at high pass crossovers and the charts for 4 ohm and for 2 ohm.  You see that the values are completely different according to the intended load impedance.  The result from this wiring configuration, in this sense, would be that the crossover would fluctuate between two different crossover frequencies.  To add insult to injury, the imaging would be severely smeared as right and left signals would coincide in the center.  Negative result:  sound like ass.

Your front soundstage problem arises from the result of the tweeter being too far away from the mid, and firing in a different plane.  I don't understand how you are pleased with sound and accuracy, but are not pleased with the soundstage...as these principles are intertwined.  Reposition the tweeters and do it without cutting holes.  Tweeters can usually be attached with a glue-type substance. 

Err...ahh... what you are proposing is not a good idea.  Here's the way to do it correctily (note that the signal comes from both + speaker outputs):

Left Speaker                                        Center Speaker                                                Right Speaker