RE: using expanding foam in built up wings
Seriously mate, don't try it.
Expanding foam does just that, it expands.
And when you think it's finished, it expands some more......then some more.............then snaps through your sheeting and ruins the remaining good ribs.
This stuff will not come away from balsa easy, so effectively if your plan goes south, your stuffed.
Do yourself a favour, remove the covering, inspect the damage with your eyeballs, and make new ribs etc if need be.
I serioulsy doubt mice would eat the ribs and leave the spars intact.
Don't risk trashing a 100" edge plus your engine & radio gear doing a dodgy fix.
Just my 2c