I not that familiar with the floorplans in GTRV's but I know that floor space in all Class B's is valuable
My RT had a bunk on either side in the rear. I think they were each 27" wide. It served as seating also. It could become a king sized bed for sleeping but we mostly used it as two "twin" beds. Water tank, water heater, furnace and electrical compartment were located under the bunks.
Do you have one bed or two? If one, is it full size?
Have you been to the GTRV Group on Yahoo?
You probably have to join but there's lots of interesting stuff.