I would suggest not getting one any smaller than that. Before I clicked the link, I immediately thought you should be getting around a 7' single, which that is just shy of, is there one slightly bigger? Are you able to take a tape measure to the retail units? ! I use a 6' single A frame for my domestics - sometimes a 7' would make things easier, other times there's no way a 7' would be viable, it depends on the space you have to work with.
I used to clean the local Homebase before they got a nationwide contract and I could use either my double or single A frame going round the outside of the garden centre windows, but it was a stretch with the 6' single. Fortunately I had all the space I needed as there was no overhang. WFP back then would've been amazing