Just tried a domestic search (holiday flights) with RPU upgrade option chosen. Outbound shows three columns: Economy, Economy + RPU, First. Of course no RPU flights available at this time so Economy and Economy + RPU flights show the same price but the RPU column shows a yellow question mark and a notification that the flights will be waitlisted. No problem. I select my outbound.

On the return ALL flights show the same three columns but the Economy + RPU column shows "Not Available". Not even the same price with the yellow icon as per above. Silly website.

I'm assuming I can book the ticket as normal in economy and apply my RPU after the fact on the old website.

-RM