Checkpoint Merge fail

[FilipeF12]

Windows 10 latest, version 1.7.0 SD, 128Gb ram

Checkpoint Merge setup:

Loaded a 7Gb model in A, loaded a 2Gb model in B. Used default settings. When clicking on MERGE, fails with error that says I am attempting to allocate nearly 400Gb of space?? What?

My disk space was too small on C: to hold a virtual memory pagefile that large, so I created 400Gb of space on an external SSD.

Now the merge proceeds, but in the first few minutes all 128Gb phys ram is used up and the machine becomes unusable (frozen).

Why should two models amounting to under 10Gb need 400Gb to merge?

TIA