And, when slingshoting, you must take the gun farther off target... But its still a good skill to practice.
As noted above, they are now teaching troops to use the slide release (while making them familiar with the slingshot method), as they've found that under pressure (in combat) that the slingshot sometimes doesn't let the slide go home with full force -- which then forces them to use the clearance drill. The old technique has created problems for troops in combat. Wearing gloves might make it worse.
(I'm sure this type of "new" thinking will be treated as sacrilege by many of the old timers -- but its based on real world results.)
I would think that a properly-shapped piece of metal, attached with JB Weld, might work pretty well... Getting that piece to fit right would be the real issue. (I do have an extended slide stop for a standard CZ, but don't know whether it would work in a 97B as the widths of the frame might be too different. I no longer have a 97B. It was too big for my hand.)