I seem to recall (it's been a while...) that the sliding lensboard on mine had a cutout in the lip where the thumbscrew went through. Removing the thumbscrew allowed it to be removed. Don't know how it is with yours, but I'm sure you'll figure it out.

I have the 375mm Ilex and it's been a good performer for me on 8x10, but with ample coverage for 11x14. It and your 240 Germinar should be a nice kit for the 7x11. The Yosemite shot above was taken with a 16 1/2 RD Artar, just for reference. If your eye is used to 8x10 (or similar aspect ratio), the 7x11 looks wide by comparison, even though it's only an inch more in the long dimension. I remember being surprised when I set up that shot that I had to go so long on the focal length. But it's just a matter of getting familiar with the format.

Look forward to seeing your photographs.