Yes, I used that same setup, and recall it was all OK.
Make sure you update the Sigma Firmware to the latest version, as I recall there were some issues before I did this.
I no longer have the 1.4x, so can't check anything else.
As an alternative, just connect your camera directly to the computer to download images. I also have the 7Dii, and do not ever remove the card.
I know there are differing views on the Forum as to the appropriate way to download images, but I prefer direct camera connection.
Bauldy
One of the great things about the Peak Design strap is it gives you options. I keep a connector on each side as well as underneath and sometimes change mode depending on the lens used or the situation that I am in.
Bauldy
To offer a different view - I have my Peak Design Slide set the same as the OP, with one side on the tripod bracket and the other on the grip, or right side.
It may differ with different camera models and lenses, but my Canon 7Dii with Sigma 150mm-600mm hangs nicely set this way and I haven't had any issues affecting the viewfinder.
As with another poster, the clamps do tend to slide down with use and needs to be re-set at times, but I have read that this was more with the original version and was improved in later models.
While I haven't tried other types of straps, I did a lot of research and believe that this model works best for me.
Regards
Bauldy