Incorrect Plate Sizing following calibration

Hello, I am using vpop to plan for TTA’s with forkless plates. The plate size is underestimating with each planning session and I am not sure how to correct it. For instance, if I have a 50lb patient the planning software will tell me I will be using a 3 plate (securos plate), but I know that in Sx that is not the case and I will be using at least a 4 plate. I measured my plate sizes to compare them to the softwares and they all appear to be accurate, so I am not sure why it is underestimating.

It is make me a little worried my cage sizes are also being underestimated. Thank you in advance for the help.

Dear Dr Eadie . Can you share a mediolateral postop and preop radiograph with your calibration marker to ? What is your method of calibrating ? How big is your marker and how to you position it relative to your patient ? Kind regards