I picked up a couple of corned beef flats yesterday and am going to make pastrami from them. Normal process is to desalt, season, smoke and steam. I'm thinking about sous vide for 48 hours at 135°  instead of steaming. Anyone ever tried this and if so is it recommended?   

Haven't tried it, but would think SV would be a great cooking method.  My experience with cuts that small say it does not need that much time, but that is extremely subjective.  I am starting to re-think my method and that the smoke should be the last thing done.

Wouldn't you end up with a bunch of juice in the bag that would wash all the rub off?  I did a sous vide corned beef once, and there was a ton of liquid in the bag when it was done. Otherwise, I'm sure it would work fine, but I LOVE steamed corned beef and pastrami so I'm not sure I could like any method more than that.

The corned beef has been desalted for a day and the seasoned meat was put in the refrigerator yesterday in order to let the spices do their thing. I'll smoke today to an IT of 125° then back in the refrigerator for 24 hours followed by sous vide at 135° for 48 hours. I would not expect the amount of juices in the bag to be any more than any other piece of meat similarly processed. As for washing off the rub, I'm hoping that the overnight  penetration will compensate for any loss. I would suspect that the traditional steaming for 3-4 hours also removes a lot of the rub.

Ready for the SV set to 134° but I'm reconsidering the length of time that I leave them in. Current thinking is 32-36 hours.

 32 hours was perfect, best Pastrami I've ever made.