Hi Raymond.
I would strongly suggest that you use system code 55 for *ALL custom objects. This will ensure that the objects are included when you install your next upgrade.
I have never tempted faith, and ignored this protocol, but JDE has assured us that failure to do so could result in these custom objects being "Lost" during the installation of future upgrades.
We successfully checked the customs objects out, changed the codes to 55, and suffered no ill-effects.
Better safe than sorry.
Sometimes, "no news, really is good news".
Joseph