removing output DC ground from Server SMPS for series operation ?

[Freelander]

I have been offered a couple of Compaq server PSU's. They are 12v output at around 500W (as they are server PSU's they only offer 12V as the main output - they are not a standard 'atx type PSU at all). The output is basically two very large tabs on the PCB offering 12V.
At the moment, the DC negative is connected to case ground, which is connected to Mains Ground.
I want to float the output to allow the series connection of the two units.
The physical removal of the DC to Case connection is not an issue (it is a case mounting post to PCB connection only). I personally cannot see any glaring safety issues at all as the units are using absolutely top class components.
I have plenty of the cheaper 'meanwell' type units - genuine and the ying tong yip types - and these are all floating outputs but I would prefer to use the far higher quality compaq units 12V units. I can understand why compaq ground referenced the DC for use as a server PSU, but when not used in that application I can see no 'obvious' reason at all against 'floating' the output.
I would be interested in the thoughts of others regarding this.
Your Input as always is valued.
Many thanks
J.