Does your abattoir have a weight limit for sows? Ours does, max. 250 kgs, above that they have to go through the cattle line, with slaughter costs about 4 times as much as when they leave the skin on through the pig bath. Worth checking out. One of ours was 240 kgs and was allowed through, the other one was 270 kgs - had tried putting her on a mini diet for a few weeks beforehand, but don't think it had much effect.
So far all our sow meat has been very tough indeed, although tasty, and the part I really don't like is the greasy, slimy fat, sort of wobbly like cellulite, and very different from the nice firm fat on young pigs which makes such delicious crispy fat when you fry the bacon. Tamsaddle