We bought a made to measure Cali carpet from a UK supplier (sorry, can't remember who) when we got the van but it was not entirely successful. Purchased the medium quality and once fitted moving the lower bed was quite difficult. It could be done but it was a struggle. The carpet was just too thick so it caught on the underside of the drawer. Also had to stick bits down with blue tack.
As Mrs DoH makes up the bed changing things wasn't a priority but, in France this year even she was having a struggle and I took over and removed the carpet. Aah! Wonderful the drawer rolled like silk. We bought two small carpets from Wilkinson’s price not a lot and now ,after 5 years she has no problem fixing the bed.
So, for what it is worth I would avoid a carpet unless your wife/partner is very strong