Toshi, I am endlessly amazed by the quality and speed you can build models. The Lancaster is a beaut!. I actually got to crawl through one last summer at Osh Kosh. I do mean crawl, getting over the wing spar was a challenge. Talking about the B-17, it would typically carry between 4000-8000 pounds of bombs, depending on how far it had to fly. As I recall, a typical mission into Germany would be closer to 4000 pounds, or 8X 500 bombs. One of the issues with the B-17 was the size of its bomb bay. It could probably lift heavier loads, but you couldn't squeeze them in. As such, with its broad wing, the B-17 could fly higher and that made it safer than the B-24, which just couldn't climb as high. THe B-24 could carry a larger load over more distance, though.
John