Reinforcing raw denim

I found myself at Unionmade in San Francisco this past weekend and ended up walking out with my first pair of raws: Tellason Ladbroke Grove, 14.75oz. They're being hemmed at the moment (Unionmade does it for free), so I've got some time to think.

What I want to do is reinforce the seat (like the Levi Commuters), as I've got big thighs and I get around by bike -- most common cause of death in most of my pants is blown out seat.

What I want to know is WHEN to modify the pants: before or after the initial soak, before or after breaking them in & stretching them out a bit? Tellasons are sanforized, but I can't help but think it would be better to stitch the double seat in after first soak just in case. But if that's the case, should I do it as soon as they're dry or should I wear them around for a while?

Thanks in advance!