How should I lock my bike in a public front wheel bike stand In front of my gym there is front wheel bike stand that means a regular D lock will not be able to  reach from the stand to the frame.

Around the corner is some Sheffield style locks but they are out of the view of the gym - meaning easier for criminals.
I am wondering what is the best approach for locking in a situation like this.
Should I invest in a long chain as a second lock to reach the frame.
Would a thin cable be suitable?
Is it better to go with a Sheffield even if it is not in front of building.
The same racks were installed &quot;temporarily&quot; at my local station at the beginning of the year. This is somewhere where a bike with only a cable lock is unlikely to last a week of commuting before being stolen.
It's often possible to put your back wheel in these racks, being careful of the rear derailleur (you may need to select a very high gear). Then a long D-lock can reach to the chainstay, possibly even through the wheel to the opposite chainstay. My kryptonite series 2 won't go through the wheel as well, but my masterlock will. I also use a cable to the front wheel. I considered using 2 D-locks, one locking the wheel to the rack, and the other locking the frame to the first, but didn't do it in the end.
Putting the back wheel in makes things a little awkward for other users - but so does overlapping handlebars when every space has a bike parked forwards. So try not to park right next to someone.