An inch worth of topper memory foam and breathable fabric made a great addition to an inch of medium firm foam and then high cell count softer foam - none of this is available in Mexico.
Upholsterer's try and recycle foam. Problem is that foam as they stuff it in is usually decomposed to the point of crumbling
Aduaneros, Mexican Customs are -particularly- sensitive about 'importing' raw foam. They do not care what it is for. Best to wrap the new stuff and hide it n a compartment. Same for the tela, the cloth. When I buy foam and cloth NOB I ask for a knowledgeable recommendation for proper thread. Tell them it's for "Heavy Duty" use.
I hate to say this but when using an 'unverified' upholsterer find some way to actually eyeball the assembled foam before the final inner covering is stitched on. Some shops are less unscrupulous than others and suddenly decide innovating a bit of your new foam with a lot of your old foam affords them with an irresistible opportunity to squirrel away the 'extra' foam -That Is of course, Obviously not Needed- some or a lot of the new foam you brought down. Foam is -expensive- in Mexico,