Converting Map Sizes (Centered)

I am having some trouble converting a 192x192 map to 256x256, and keeping it centered rather than in a corner. The Blizzard editor doesn't seem to allow conversions to 256x256 even though you can create maps at that size. I tried the Zepir editor, and converting to 256 with it creates the extra squares always north and east of the existing map, unless there's a way I don't know about. Even so, I tried to change the 192 to 256 in the Zepir editor, then open the resulting map in the Blizzard editor, and change the bounds there, without changing the size (in order to recenter the original map area). Still it would not let me. There must be a way to do this. . Three questions, then. Can it be done with existing editors, or is it necessary to open the w3m and files therein? If the second, is it relatively simple to carry off, or less so? Last, how is it done?

Forget about opening any file in the W3M. If you wanted to recenter your map it's the W3E and if you had a look to its format, it'll not be easy to edit!
I'll add more features to my map resizing tool, just give me time...
You'll be able to recenter your map (offset) or to scale it,...

Thank you.

WE allows for copying and pasting. I dont know if it will move everything at once(units, regions, terrain), but it shouldn't take more than a few passes.

Hey you're right. I had tried to multiple select objects with shift or control, assuming that if anything would work, that would. Since you mentioned it, I just tried multiple selecting objects by dragging. So incredibly obvious. :( Yes I feel stupid now. :) Thank you.