01 What makes it unique
The 388MBS is the Solitude built for families who want a separate place to put the kids. Its defining feature is a middle bunkroom — a dedicated bunk zone amidships, between the front master suite and the rear living area — rather than a second full bath. The back of the coach holds a rear living area with rear entertainment, and the whole plan sits under a lower 12-foot-9 roof on four slide-outs, a half foot shorter than the 13-foot-5 standard plans for easier garage and overpass clearance.
It is one of the heavier standard plans at a 15,985-pound dry weight, reflecting the bunkroom and the longer 43-foot body, which leaves a 3,015-pound payload and a 2,930-pound dry pin. RVUSA lists a published 19,000-pound GVWR on the standard Solitude build — the 101-inch widebody drop-frame chassis, a MORryde pin box, a heated underbelly, 330-watt roof solar and a 20-cubic-foot 12-volt refrigerator — with a single 15,000-BTU air conditioner standard. A 53-gallon black tank serves the single bath.
At an MSRP of $163,220 it sits among the upper plans. For a family that wants a dedicated bunkroom rather than the two-full-bath 391DL’s second bathroom — and a lower roof line — the middle-bunkroom 388MBS is the family Solitude on the standard 19,000-pound chassis.
02 Full specifications
Dimensions
- Exterior length
- 42' 11"
- Exterior width
- 8' 5"
- Exterior height
- 12' 9"
- Interior height
- 8' 0"
Weights
- Dry / unit base weight
- 15,985 lbs
- GVWR (max loaded)
- 19,000 lbs
- Net cargo / payload
- 3,015 lbs
- Dry pin weight
- 2,930 lbs
Capacities
- Fresh water
- 81 gal
- Grey water
- 106 gal
- Black water
- 53 gal
- Refrigerator
- 20 cu ft
Construction
- Frame
- Drop-frame · 101" widebody
- Walls
- 5-side aluminum cage · laminated
- Roof
- Walk-on TPO · limited-lifetime warranty
- Underbelly
- Fully enclosed · heated tanks & storage
Running gear
- Axles
- 2 (8,000 lb tandem)
- Hitch
- Fifth-wheel (in-bed) · MORryde® pin box
- Suspension
- MORryde® CRE3000 · Tow Assist ABS
- Tires
- 17.5" H-rated Cooper
Galley & bath
- Cooktop
- Professional-grade SS · built-in oven
- Refrigerator
- 20 cu ft
- A/C
- 15,000 BTU (single)
- Water heater
- On-demand · whole-house filtration
Sleeping & layout
- Sleeps
- 5
- Slides
- 4
- Awnings
- 2
- Primary bed
- King
03 The Solitude floorplan family
Solitude is Grand Design's flagship fifth wheel and one of the best-selling luxury extended-stay fifth wheels in North America. The line runs to ten floorplans for 2026; the eight highest-demand layouts are profiled here in full, and the remaining two are catalogued on the line hub. The 388MBS on this page is highlighted; each other profiled plan links to its own page.
| Floorplan | Nominal | Sleeps | Notable |
|---|---|---|---|
| 310GK | 34 ft | 4 | Light rear-kitchen entry, sub-13k dry |
| 370DV | 38 ft | 4 | Rear living, central island + prep bar |
| 380FL | 41 ft | 6 | Front living, bath-and-a-half, 5 slides |
| 382WB | 41 ft | 6 | Separate front living room, 5 slides |
| 376RD | 42 ft | 6 | Raised rear den, three sofas |
| 390RK | 42 ft | 6 | Rear kitchen, outdoor kitchen, 5 slides |
| 391DL | 42 ft | 8 | Two full baths, dual entry, sleeps 8 |
| 388MBS | 43 ft | 5 | Middle bunkroom, family, lower profile |
| 417KB | 42 ft | 4 | Rear kitchen, bath-and-a-half, master |
| 414LJMJ | 43 ft | 6 | Triple-axle flagship, mid bunk + loft |
Solitude is Grand Design's flagship extended-stay fifth wheel and one of the best-selling luxury fifth wheels in North America. The full line runs to ten floorplans for 2026; eight are profiled here and two more are catalogued above. Every plan rides on the same drop-frame 101-inch widebody chassis with a MORryde pin box, 8,000-pound axles and a fully enclosed heated underbelly, and ships with a 330-watt roof solar package, a 20-cubic-foot 12-volt refrigerator and an on-demand water heater with whole-house filtration as standard. Body specifications (lengths, heights, payload, tanks, sleeping, slides and awnings) are RVUSA-verified against the 2026 structured spec records, each page fp-slug and title checked; dry weight, GVWR, payload and pin weight are published per plan, and each plan's dry weight plus payload equals its GVWR exactly. Real loaded pin weights run higher — always weigh the loaded coach and confirm against your truck's payload and rear-axle ratings.
04 What owners & reviewers report
Middle bunkroom
A dedicated bunk zone amidships between the master suite and the rear living area — a separate place for kids or guests.
Lower 12-foot-9 roof
A half foot shorter than the standard 13-foot-5 plans — easier garage, overpass and storage clearance.
Rear living + entertainment
A rear living area with rear entertainment behind the bunkroom — a family layout that keeps the main lounge at the back.
Heavier standard plan
At 15,985 lb dry with a 3,015-lb payload, it is one of the heavier 19,000-lb plans; confirm a properly rated 3/4- or 1-ton truck.
05 How it compares
The two-full-bath family plan — a full second bathroom and sleeps eight instead of a middle bunkroom.
The triple-axle flagship — a bunk-and-loft on a heavier 23,500-lb chassis with the largest tanks in the line.
Keystone’s middle-bunkroom-and-loft plan — the direct big-luxury-FW cross-shop.