Easy fix mate. All our dozers get a couple of pieces of hollow bar welded to each section of the belly plate, with matching pieces on the frame. When you need to access inside you just slip in a pin to work as a hinge, put a hydraulic jack under the other side and undo the bolts. Then lower the jack, do the job and jack it up again. The plate just swings down to the bottom of the jack stroke on one side which gives room to get in. Hinging allows for easy alignment going back up, and means it cant slip off the jacks and squash you when you're dropping the bolts. I can lower any section of belly plate on one of ours, hose the dirt out, and have it up again in 30 minutes.
WARNING: Remove the pins when not in use. Otherwise if you do hang up and warp the plate you'll have to cut them out. And that's a nasty job. And leave enough room between each section of hollow bar for some movement.