Im not sure what your issue is. In Colorport, you select what measurement device you are going to use - this defines the minimum patch size in mm - color space, then the patches you want (either your own or one of the presets) and then the paper dimensions, orientation and margins. If minimum patch size is defined, and presumably for good reason, then apart from adjusting margins on A4 paper the only variable is how many rows/sheets you need. Is that a big deal?
My problem is that for isis for example with default settings the only target that fits in A4 sheet without borderless mode is PM5 generated targets. All other software can't squeeze the same amount of patches without forcing you to use borderless mode for printing for target to fit into A4 sheet.
No software provides means of measuring the exact printed target dimensions, and that is PITA.
I looked at various targets in PS:
For example PM5 targets are 822px x 1190px at 101.6dpi
basiccolor targets are 2480px x 3508px at 300dpi
colorport targets are 1680px x 2344px at 80dpi
Now if you know anything about image resizing you know it's near impossible to make a target like colorport to be exact dimensions of PM5 target, that is 822x1190px at 101.6dpi (one of the problems being photoshop has a linked document size and pixel dimensions, the other being that from size of 2x larger even with nearest neighbor resize I get distorted patches.)
In other words what I'm trying to say that gretagmacbeth was clever enough to make PM5 generate targets that match the
1. target dimensions in pixels
2. document size