baffle layout of L300-type speaker

I have a 4-way system consisting of one 18"-woofer in one box, and on top of that one box containing one E145, one 2441 with tractrixhorn and one 2405. I'm on my way to build the final boxes to use instead of these testboxes. I have a few questions regarding the layout of the drivers on the baffle on the top-box:

*What do you gain in having the mid's and high's an inch offset from the woofer's mid-line (as on L150 f.e.)?

*Should You try to get the drivers as close to each other as possible?

*Could there be trouble in the mid and high area since the 2405 and tractrixhorn of the mid doesn't share the same dispersion etc.

Todays testbox has this layout: woofer - UHF - 2441 in line (they all share the same mid-line. It is approx. 20" from the woofers center to the middle of the 2441.) I'm rather happy with them, but as this will be the final boxes, I must be sure they sound as good as they can!

Grateful for any input!