So would you still need to do the initial run off? Why mash in the boiler? Looking at Jim's setup I would have thought that it would be better to just mash in the lauter tun? Or is the temperature adjusted during the mash?
When I did extract brewing, I used a mash bag for steeping grains and some bits still escaped that even with the fine mesh. Surely this means there would still be the need to get a clear run off before sparging?