Kayleys Mom, when we were at the factory service center with our unit, we asked about it. They said that because the bumper is no longer welded on, but just bolted on, it would not take the weight of a mounted spare tire (around a hundred pounds).
They said that if we wanted, we could have extra supports welded on, but they wouldn't recommend altering the structure while the unit was under warranty.
But, if you have it in writing from Jayco that the bumper on your unit will take that kind of load, then why not. Just remember that it has to be centered, so that there isn't an asymmetrical load on the bumper support structure.
Good luck and safe camping!
2018 Jayco Alante 31v
Me, Dear Wife,
2 Bluetick Hounds
1 Newfoundland / Black Lab Mix
1 Cairn Terrier