I’m cant speak for a HiLo roof, as I have an SCA roof, but I can’t leave my sea to summit up there when the roof is down, even if deflated unfortunately.You may struggle with space in the HiLo, depending on how flat that mattress will go.
@Ozi, @russ_e or @Honest_Bertie mught be able to tell you this as a search shows they’ve bought the same brand.
I’ve got a SWB HiLo Sport and think the bed measures 118cm wide, but this was fitted in 2017 so may well be different to their current spec. Whichever you choose, you won’t want the mattress touching the sides as it may bridge and subsequently bring in damp.
Here’s a cheap and simple solution:
But it’s a great mattress, and well worth the investment. I just tend to roll it loosely when deflated and put it on the parcel shelf behind the seats.