6.1 Ocean upstairs mattress - use downstairs?

[PhilR]

We fully intend to always sleep upstairs as only 2 of us. However, when it’s not suitable due to severe weather for example, we’ll sleep downstairs. We haven’t ordered the comfort mattress due to the space it takes up considering it’s intended lack of use. Looking at all the videos of self-inflating mattresses, they seem like far too much hassle. So for the very rare occasion, could we not just use the upstairs mattress downstairs? Yes I know it’s technically too big, but as it’s not too thick and fairly flexible I imagine, won’t it do? Not really seen this mentioned so would be interested to hear thoughts.
By the way, haven’t got the van yet in case you’re wondering why I haven’t just tried!!!