Is it the Slimrack system? My understanding is other brands advertise that it is OK but I'm not sure about Grand Design. I would email Grand Design and let them answer you in writing. It really is their call. Especially if something happens and you need to get it covered under warranty.
All slideouts are MUCH weaker when retracted. Some like my fridge slide have wheels to support more weight when retracted. I have never seen a bed slide that had wheels to support it while retracted.What does your owner's manual say? Sometimes salespeople are not as knowledgeable as one would hope.
Mine has four rollers screwed into the foot end of the bed box - one on either side of the box about 2-3' from the toe end the other two under the pull-out seat/storage box. All rollers ride on the lino - have the indentations to prove it. Rollers are about 2" wide and provide great support to be on bed when retracted.
When you say "while traveling" do you mean stopped while traveling? or while bombing down the road? First there is nothing that should prevent you from sleeping on the bed with the slide closed moving or stopped. That being said as a retired state trooper, although it's perfectly legal to do so in about half of the states in the US, as long as you have a way to communicate between the driver and passenger, I would not recommend it for a minute. If you've ever seen a trailer that has come apart in a crash you'd know that even a minor accident could result in an overturned trailer that comes apart like a soaking wet cardboard box in a hurricane. Rarely does the passenger come of it well.
We are on our second 337. The first a 2018 and now a 2025 and have slept with the bedroom slide in on both without any issues. We’ve done it for quick overnight stops or when we have been in very windy areas where we thought our slide toppers were going to rip off the rig.
As someone who has had to have their slide rack replaced twice, my advice would be to don't mess with your slides. As I understand it from researching slides, your slides are designed to ride all the way in and are only to be used when the unit is leveled and the slides are all the way out. Plus, I don't think it would be wise (or legal) to have someone in your trailer while traveling. Passengers should seat-belted no matter where they are traveling.
Do you remove the stuff in your underbed storage before operating the slide?
In the 260RD, the slide has the pantry, refrigerator and the couch. We do not empty the pantry or the refrigerator. I suspect the weight of the refrigerator near the one end of the slide may be the issue in the 260RD or maybe I just have a lemon. Probably a design issue. The stuff in the pantry is pretty light except for a few cans of canned food that may be kept in there.
.I do it in my 2020 337RLS because I fail to see the difference between my body weight and what someone might be storing in the bed compartment under the mattress. I only have an ironing board, iron and an extra blanket. I've seen others stuffed with clothes which weight wise can add up quickly. It seems to me if there was an issue, you wouldn't have storage or such a large storage space under the bed. Especially because whatever is in there is bouncing down the road while traveling possibly putting stress on the slide mechanisms.
