2" foam is too thin for comfortable sleeping. 4" is minimum. Don't cut corners now since a couple extra inches of foam is not that expensive, even if you don't plan on sleeping on the settees or quarterbunks now. You might later on, or the next buyer might decide that having to get new cushions for those bunks makes his bid lower when you decide to sell. The expense and/or work is in the upholstering and the difference in cost of a 2' or 4' inch thickness is negligible.