Hi mrstweedle,
Congratulations on your new mattress 
As you know I think you are making a great quality/value choice and I’m looking forward to your comments and feedback once you’ve received it and have had the chance to sleep on it for a bit.
It would be OK in terms of providing good support for the mattress but there would be no airflow under the mattress which along with any other risk factors that may be present could increase the odds of developing mold or mildew under the mattress (see post #10 here).
It should be OK in the short term as long as you check the bottom of the mattress on a regular basis and give the bottom of the mattress a chance to air out from time to time (say once or twice a week) either by flipping the mattress over for the day or by standing it on its side (without any sheets or bedding on the mattress) so that any moisture or condensation that is trapped in the mattress has a chance to evaporate.
It may also be a good idea to put a wool blanket under the mattress as well for the time you are using it on the floor.
Phoenix