As a wrap up to this thread if anyone uses it for reference down the road.

This is probably a rookie mistake, but it's important to note that VFP's "ThisForm.Width" and "ThisForm.Height" reference only the inner portion of the form, not the titlebar and window borders. The WM_SIZING rectangle values for the form DO include these items. You can add SYSMETRIC(9) + (SYSMETRIC(4)*2) to your ThisForm.Height value to match and add (SYSMETRIC(4)*2) to match your ThisForm.Width value.

If you're doing percentage calculations from a component inside the form to the form itself, these differences can really throw you off.