Why not put a few racks on the bottom grate then more on the extender in the middle then stack the roast rack on top also filled? You may be able to squeeze more than you think. If you can minimize contact more racks don't necessarily take longer.
I almost never use a drip pan. My plate setter has had drippings on it for years. It's nice and seasoned and when the temps are high it sears the drippings and adds more smoke. I wipe/scrape it before a cook and every now and then I'll leave the egg on for an hour or so after I'm through to let it "oven clean". After this my plate setter looks almost like new (except it's completely black) but there's no gunk build up or deposits on the indirect side. You can still clearly see the bge graphics in relief.
Now the side down to the fire takes a bit more to get clean and I can not use it to bake on due to the scale but that's what the stones are for.
I like the drippings-added-smoking offered for some cooks by letting the plate setter do it's thing "au natural"
I use a drip pan with apple cider vinegar or other concoction to add flavor and avoid grease fires when needed.