If your protein wont aggregate (or precipitate) with lower amount of detergent, I would say try incubating the concentrated protein in Biobeads to remove some of the concentrated TX-100. The removal of TX-100 can be easily monitored by UV absorption or fluorescence as TX-100 does absorb around 280 nm wavelength. I have not come across the mixing detergent technique, so that sounds interesting as well. If this indeed decreases your micellar size, a good way to check would be using light scattering I suppose! I hope this help! Good luck!