NYC 4-6-4 Commodore Vanderbilt Hudson.
Testing engine on my minimum 48" curve with lower front skirting 'in place'.
The wheels are really close to the skirting on 48" radius but it did negotiate the curve.
To be 'safe':
1) I used canopy glue to secure the skirting as there are only two small round tubes that go into the 2 holes in the boiler plus they will be easy to remove with the canopy glue.
2) I filed the inside of each skirt to give the wheels some extra 'room'.
A 'rounded' file was used.
All moving surfaces, also, got lubricated.