Hi IT_Guy,
There are some extra challenges when you are doing mattress surgery with a two sided mattress.
As you probably know I would consider mattress surgery as a last resort when there are no other good options (see post #4 here). While it’s unlikely after 10 years … if the foam in your eurotop is still in good condition with no or only minimal soft spots or sags then a different topper may be a good solution (probably thinner than the one you’ve tried already). After 10 years it’s also possible that the springs may no longer be even or may have shifted although that’s less likely than an issue with the foam so you will need to test them to make sure they are still good.
I would start with some “exploratory” surgery on one side by removing the quilted cover at the top tape edge. This will give you access into the contents of the Eurotop to see what’s inside.
You will probably need to remove the Eurotop from both sides because if the foam is sagging or has softened then this can come through to the sleeping surface and if you test the springs with sagging foam under them you won’t know where the sag is coming from.
If you remove the material in the eurotop from both sides (but leave the eurotop compartment and the foam below it in place) then you can replace the foam in one side and trim the material in the side panels of on the other side and use it on the bottom of the mattress to turn it into a one sided mattress. If you remove the Eurotop on both sides then your side panel wouldn’t be attached to anything on either side and would be loose and the mattress would have little structure.
So step 1 would be to remove the quilt panel on one side of the mattress to see what’s inside it and then if it seems worthwhile continuing I would remove the foam in the eurotop on the other side before testing the springs through the foam that is under the eurotop which would remain (see post #8 here about testing the springs) to make sure they are still in good condition. Removing the seams on 3 sides should be fine to give you access to the eurotop compartment if you plan to keep the quilt panel (assuming it’s also not too thick and depending on what is inside the quilting because it could also be the cause or at least part of the problem).
Phoenix