QTR-Quadtone RIP

Hi, thanks to you guys I was able to get solution for my problem. I have build DTG printer from EPSON 2200 and I wanted to print white underbase on dark garment. I was able to setup QTR to print white using Lb, Lc, and Lm. Color image I was able to print from GIMP using Gutenprint and with CMYK channels. I have a little problem with registration since I have to print from two diferent programs. I am wondering if you guys can help me to fix this problem.
Does anyone know if I can print image using gutenprint and using Lc,Lm and Lb. Sice i would be using white ink in those channels I just want to put as much ink as it is possible. I dont know is this possible or not since I would have to tell printer to use only 3 channels to print image. I dont know is it possible to build profile in gutenprint to print any image using Lc, Lm and Lb. This way it would be great to print white underbase and color image on top using just one program. This will solve registration problem.
Thanks in advance