I believe the major difference is that RR is a "Raised Rail" while M is not. I have a Santiam the bay area does not move with the slides, I have a freind that has the Monterey, the bay storage area on the drives side moves with the slide. He does not have the basement stroage. At least that is what I have noticed when we are together.
Happy RVing
John and Judy
US Air Force - Retired
05 Beaver Santiam 40DST
08 Malibu Toad/Brake Buddy
Here is the link to the Roadmaster chassis website. Should be able to find your answer here.
Bob & Betsy - USN Ret'd '78 & FL LEO Ret'd '03 FMCA #F203528 '05 HR Endeavor, 40PRQ (Our Home) w/400 Cummins - With -'05 GMC Sierra SLT, CC Z-71, the pusher- With -
'07 Arctic Cat 500A & Wilderness Kayak, riding in the pusher - Our Current Location