We at Strathaven are in the restricted area. We - like Cumbernauld - have an "exemption" allowing almost usual operations.
To be frank, unless you want to fly into the Glasgow zone (or a section of the Class G out to the east, plus the odd little bit over the shooting range out by Dundee), it is almost business as usual.
So it is just like transiting around a bit of controlled airspace - which you should always plan for, anyway, in case you get refused a transit. The bit east of Dundee
is just like having a Notam out for something to be avoided. No big hassle.
The two differences for Strathaven are:
All aircraft (home based and visitors) must have PPR. And that PPR must be at least an hour in advance if you want to be certain that the airfield will be open. Since Cumbernauld already requires PPR and has published opening hours, that is really no difference there.
Second, there is an entry/exit lane into Strathaven and Cumbernauld. Details available when you ask for PPR. In Strathaven's case, directly from the south.
Finally, you can apply for a restricted zone transit by phone, just like Glasgow like you to do in "normal times". However, this time you'll need a whole load of info - like your cat's DoB etc, so personally I wouldn't bother. Just route around.
ps Glasgow ATC have asked local airfields to point out: the eastern boundary of R503 is quite a bit to the east of the Glasgow Zone. (In fact, as I see it, either you fly under Edinburgh's stub, or ask them for a zone transit)