Question about calibrating VNA

Hi, I want to calibrate the VNA for S11 setup and I have a calibration kit with SMA connectors but the last piece in the cable has a different connector. It looks like this:

VNA --> APC7_adapter_SMA --> SMA_cable_SMA --> SMA_cable_custom

To show you this "custom" cable, here is a link:
https://www.digikey.com/product-det...orth-america/MXHQ87WA3000/490-7212-ND/3909120

There is no way I can get a CAL kit for this type of connector.
So here is my theory:

With a perfect match, the length of the cable doesn't matter, otherwise the length is very important.
So I was thinking to do the 50-Ohm load calibration without this custom cable like this:
VNA --> APC7_adapter_SMA --> SMA_cable_SMA --> SMA_CAL-LOAD

Then even though I have calibration short and open standards, I can't use them on the custom cable, so that I would make my own little open and shorts that I can use with the custom cable, like this:
VNA --> APC7_adapter_SMA --> SMA_cable_SMA --> SMA_cable_custom --> custom_CAL-OPEN
VNA --> APC7_adapter_SMA --> SMA_cable_SMA --> SMA_cable_custom --> custom_CAL-SHORT

Can I safely assume the following three points?
Due to the small size (a few mm) of the custom connector, my home-made open and shorts should not mess very much with the calibration, so that the home-made open and shorts will still provide pretty darn accurate.
That I can have faith in the "custom" cable being close enough to a perfect 50-Ohm that my load calibration without this cable is pretty darn accurate.
My theory on calibrating this setup is correct.

If this is not true, how the heck would you calibrate something like this with no calibration kit available for the connector type?

Many thanks for any answers!

Suitable calibration means have to be related to the intended accuracy and frequency range.

For moderate accuracy requirements you may do everything with port extension. But you'll see losses of the thin SWG probe cable.

My preferred solution would be a self-made SOL calibration adapter using a small chip resistor for 50 ohm load. I have a similar adapter with three U.FL connectors to calibrate a measurement setup for RF devices with U.FL antenna or test connector.

You can check the accuracy of your open , short config using smith chart. Other option is to calibrate with standerd kit and apply port extension.