-
I ended up managing to undo the bolt a tiny bit so did that, soaked it in water that was warm when I started but I left it in there soaking for a good 24hrs I think so obviously the water wasn't warm for long.
Stuffed it full of newspaper and wrapped some toestraps around it and let it dry in a warm(ish) room for a couple days, kept checking it and smooshing the newspaper and leather into the shape I wanted.
Heavy coat of Proofide once it was dry.
The results, it's a lot less lopsided but probably not 100% symmetrical. An awful lot more comfortable - it was pretty much un-ridable before.
Re tieing, I have another one I've done this to, didn't block it just tied the sides in as they were quite flattened out when I got the saddle (another 2nd hand ebay one). Its worked alright, the shape isn't the usual flattish top and verticalish sides, more like an 'O' sort of shape now but its comfortable, I rode 48 miles of gravel on that saddle last weekend .
Hey!
re: the tension bolt -- the fact it's never been used is probably the reason the saddle's sagged in an uneven way (also CocknBalls obvs). They do sometimes do that where there's a ridge along the middle (seen it a lot on Swifts). Might be something to do with the leather, it varies lots. B17s are pretty thin stuff these days - it's basically the saddle flattening where the sitbones are, and not where the bumcrack was (sorry ew). For this reason consider seriously the option of tieing the side skirt flap things down/together once you've tried to restore the shape. You punch some holes either side, and lace it up.
No bother loosening it if you can't, just be sure add some once you've blocked it and dried it so it keeps taught and doesn't immediately sag again. When it's been wetted, just be sure to really stuff the shit out of it, improvise something to keep the stuffing in place (like some leather belts) if needs be.
I always use lukewarm water, and dry it out somewhere warmish too (window sill), but not hot like on a radiator.
Not tried the ride it when wet route, seems like a way to make a saddle that's rock hard shape to your sitbones a bit, not a way to make a saddle that's been saggy no-longer-saggy. But it could be good when the saddle's nearly but not quite dry I guess. Neatsfoot would be a safer route.*
*re: the above
Use neatsfoot with caution, i.e. much less than you think is necassary, as it can really soften the leather a lot.
Sorry this help is late, you may have already done it. Thanks to @wildwest for bumping while I happen to be on here.