If you havent done it, do yourself a favour and get it done, even if there are no cracks, its a huge mission to fix it if its too late.
I repaired my cars cracks this week. I think the floor should have been replaced but due to lack of skilled workshops and because I couldnt find anybody around here that has done it, I did it myself.
I got the turner plates and I did the Structure/cavity foam. Drove it with the rear seats out after letting it stand for 30hrs and heard a squeek (another crack below the rear seats) welded that up and finally its solid again...
I wish I just did the foam before all the cracks. If one mount fails it puts huge preasure on the rest untill they also fail....
I have pics to prove it.....
Left rear mount
Right Front mount
Left rear
right front
After welding

After sealant and Primer
Inside cracks where squeek came from

I am also going to fill cavity's right under the inside weld with a hard rubber compound just to be safe.