After checking it really is the same size (no 650B stuff) then just ensure that all the the wire is in the middle of the rim [_II_] like that.
Most rims have a deeper middle, this allows a little more movement to get a tyre on.
Just be a little realistic, due to production variences some rim/tyre combinations will never work. I am reminded of the battles of Rigida Laser 400 Ano vs Specialized Nimbus 1.15
In the end I gave in, rebuilt the wheels with Mavic 117 SUP CD and they were super.
Somerset, like 'Heartbeat' with newer cars!
Retro MTB: 1992 Cannondale 3.0 Deore XT M730. 1992 Marin Pine Mountain Deore DX M650.
Retro road: 1992 Eddy Merckx Corsa Extra Telekom Shimano 600 STI. 1993 Dyna Tech Ti.
Modern: 2006 Wilier scandium Ultegra 6600. 2014 Wilier GTR Ultegra 6800.