OP updated, PM's being replied to as quickly as I can.

DPS-2000BB PSU's are out of stock and unavailable to me at the moment, so PSU packages are only available without PSU's for this time.  I still have many IBM 2880W PSU's in stock, and can use them for GPU packages as well.

To answer your question, 4250W at the wall at a 90% efficiency is only 3825W DC, or 95.6% load.  It is heavy, but with sufficient cooling it can work.  Heavier loads can impact PSU longevity, but unfortunately with these PSU's there doesn't seem to be any consistency in what that load is and if/when they will fail.  I have seen many of these PSU's run at over 100% load for extended period of time with adequate cooling, and I have seen them fail under moderate loads for no reason.