realforce 86u 87u r2 users please help

[rf86u]

I have 2 86u and plan to upgrade to 87u or r2.

are 86ub and 87u keycaps exactly the same size except the space bar? interchangeable?

are 86u and 87u keycap areas the same size?

are 87u and r2 keycaps the same size? interchangeable?

are 8u7 and r2 keycap areas the same size?

Thank you

[Sup]

Rf86u has a tsangan bottom row while the 87U has his own non standard. Just to say no the bottom row is incompatible.