For LR and CM, you can set up a master file in LR, say a 4x5 grid os 10x12" images with a 1/8th gap between them (assuming you've got a 44" or bigger Graphtec). This gives apprx 41x61 print>cut area. Paper sizesize in LR 44x47ish. Print to jpeg, then take jpeg into illustrator, and draw boxes for the cutting lines around the 10x12's. Add crop marks in CM. Discard the images in in the master file, so you only have the crop marks on the canvas. Save this as a jpeg, and use it as a graphical identity plate in the lightroom print module.
Select sets of 20 (or what ever template you build) of 10x8 files, and print to jpeg. Use the "master file" in illy call up the cut path, and to read the crop marks
If I've remembered this correctly, this should allow you to print sheets of images that you can then cut in Il>CM. I've done this a few times with vinyl jobs, contour cutting, not perf, where I've had to make many multiple sets with differing images
For only 300, if you're not running a rip, I'd make an identity plate with internal cut corners, and gang up as above, without the the illustrator > graphtec part. Then trim into strips with a scalpel, and onto the rotatrim. Depends on the paper being used. I'd consider doing this on 36" rolls, just to help the accuracy of the cross cuts, before sliding down the rotatrim fence.