| A string change, plus set up is a variable I wouldn't want to introduce into the studio evironment, especially if someone is paying for the studio time.
As big a flatwound fan as I am, I'd opt to string with rounds, and let the engineer try and shape you a flatwound tone. A bit of foam for a mute will help to get some flatwound decay into your tone. I just recorded a tune with a roundwound strung jazz..... when all the tracking was done, and I started mixing, I realized I should have stuck with my flat strung P for the song. A bit more bump in the low mids, and a little bit more cut in the highs, and it sounds like I did it with flats. I tried gating it a bit to get a bit more of a quicker decay, but opted out of that, because it sounded good without it. | 
