A Tripp-lite Keyspan Adapter that is the brand name, is guaranteed to work with the value cutters like the Pcuts The value cutters have a cheap Chinese chipset. Your RS232, connector, could very well be equivalent to the the same cheap Chinese chipset.
In Flexistarter go up to Properties in upper left corner, then click the last tab that looks like a blade.. If not done, change the packet size to 1000 kb. Click Apply ok.
For the size difference, Go to resolution and add a step. Click Apply and ok. Cut a small square that measures, 3 Inches, or whatever.. Make sure it is cutting that. Adjust the resolution to get it. Write the number down, so you know which way you went.