True thats what limit and home switches are for. The bumpers are there for when all other means of control fail, to keep your machine from flinging part of itself on the garage floor. The CRP machines could concevable, without bumpstops, throw the entire gantry off the rails and onto the floor. Assuming some very catastrophic failure in the electronics/program being run on the machine.
Bob your machine is looking great, and oversize holes are not compensation. Those are an adjustment "feature"