You've hit on the crux of the flarepod modification! Our bed platform height is as yet undefined. I believe it is going to be about 4-5" below the lowest level of the flare pod level, but unsure as yet. I'm going to let SMB West decide that, based on sitting height and access to the storage underneath.
A large factor will be access to the (former) couch/settee areas, which will now be enclosures for all the systems.
1. Drivers side has water tank/pump and D5 heating system
2. Passenger side has electrical.
I'm going to cover that at some point in my build thread and why we went this way, but a large part of it is that we never use the couch/settee as it was designed. It's always made up as a bed. In addition, during the day it becomes a catch-all for cloths, packs, etc.
In addition, since the bed is permanent, why not have a very comfortable mattress going forward? We've slept on sleeping pads, including ultra-light thin pads for climbing, for years. And really this is my wife Alison first driving this when we started out in the van. It took a while for the light bulb to come on for me..
The standard SMB cushions for the couch and bed are pretty hard, which I was initially OK with. But we then, at Alison's insistence, put a 4" memory foam medium-soft mattress topper on that, and since then it's been the best sleep we've ever had while out camping. Don't get me wrong, we still backpack and climb using a very light sleeping pad, but having a sleep system that is equable to what we have at home in the van is just wonderful. Van sleeping is VERY comfortable for us right now. It's difficult to get out of bed in the AM...
That's the lead-up to the below.
The new permanent mattress is going to be a custom mattress, exact fit to the space, exact depth as we need. Either a custom temperpedic mattress or a memory foam mattress with the FROLI spring set underneath. We're not sure yet what it will be, it's going to be based on the bed platform height.
If the bed platform height is set underneath the flarepod height, we'll have a custom mattress fit to that space up to the flarepod height, followed by a memory foam pad and topper of 2-3" above that. According to Sonya at Flarespace, we can't put a 7-8" matress on the platform as it will then be up to the window height, or at least close to it where we would impede the windows.
We are also modifying our overhead storage so we can then sit-up in the bed on one side. Probably the drivers side.
Attached is a picture of what our bed looks like now, which will give you some idea of what we've done with the bed as it is now and why we want to turn the bed transverse,