Something else worth noting. If you cannot get rid of the large raft in the middle, you can always plop something in the middle. Take a look at the following:
These are two completely different STL’s I have from 2 different projects. I have printed them just like this a couple of times with no issues. Supports can be generated separately or all at the same time.
Preform is smart enough (or dumb enough, I’m not sure which) to know the items are not overlapping but allow the rafts to overlap.
Taking it one step further, you can also put an item under an enclosed item such as this:
Cheers