[JRTJH]

I think you're on the right track with your calculations, but there are a couple of considerations you need to "crank into" the figures for all Keystone products and possibly for other manufacturers. (I don't know exactly how other manufacturers arrive at their published specifications for their trailers).

On Keystone products, the following is true:

Shipping weight is the empty weight of the trailer without options. If you add/delete anything from the ordered trailer, the shipping weight will change. There is a yellow tag on the roadside front corner of the trailer with the weight of the actual trailer along with its maximum payload. All models of the same trailer brand do not weight the same depending on options on that unit.

Tongue weight/Pin weight is the empty weight of the unit with EMPTY propane tanks and no battery or cargo. The dealer will fill the propane tanks and add at least one 12 volt battery to the unit, so the tongue weight will increase by about 100-150 pounds depending on size of propane tanks and batteries installed.

Calculating tongue weight is best done based on GVW. So, if the trailer has a shipping weight of 4800 pounds and a cargo capacity of 1200 pounds, even if you're going to only load 700 pounds, calculate at the GVW. You never know when you'll have a snow load on the roof or have to tow to a distant dumping station with a full black or gray tank. So do your calculations based on GVW not on "preferred loading". In this case, it would be 6000 pounds.

It is "generally accepted" that most conventional travel trailers tow "best" with a tongue weight between 10-15% of the total weight. With your "relatively short wheelbase Sequoia (compared to a longer truck wheelbase), you may find that you need to add a bit more weight to the tongue for it to track behind your tow vehicle without inducing sway. I recommend you calculate the "high/low range" of the accepted weights. You'll probably fall within the range, but I wouldn't calculate the "best case only" and then find you can't tow at the low end and will be overloaded with anything higher. That's a "sure fire way" of overloading your truck. So, with a GVW of 6000 pounds, the tongue weight should fall between 600-900 pounds (10-15%). Add the weight of the WD hitch to that figure to get your "tongue weight" that will be added to your tow vehicle payload. In this example, the tongue weight should fall between 700-1000 pounds when the hitch is added. I would recommend your consider the "heavy end" so you "know you'll be safe" with any adjustments you might need to make to improve towing.

Usually you can pretty much "count on" being around 12% of trailer weight, but each rig is different. Tire resistance to side roll, vehicle loading, trailer loading, height of hitch, front axle/rear axle performance, CG of tow vehicle/trailer, side winds, road crown ... the list goes on and on with regard to what affects towing..... Change any one of them and performance could (not will) be affected. Consider that a shift to a lighter or heavier tongue weight may be necessary to get best towing capability for your specific rig and you can understand why having a "best window" of 10-15% give you that adaptability. Don't lock yourself in by only calculating the "low end" of an underloaded trailer. Consider that you may have to adapt loading to maximize performance. This is especially true on shorter wheelbase tow vehicles. Your Sequoia, with a 122" wheelbase is in the "short wheelbase" category. To compare, a F150 CC with 6.5' bed has a WB of 150.5".

Most people do recommend you consider a "safety margin" in your calculations. Many will suggest 10%. I recommend 20% when buying a new trailer. To put that into perspective, if you consider your payload of 1380 pounds, 10% is 138 pounds. If your 10 year old son wants to bring along a friend and his bike, at a 10% margin, you're overloaded. That's why I recommend a "newbie" calculate on 20%. There are a lot of "unknowns" for a "newbie" that usually don't get considered when doing the calculations. Things like tire jacks, lug wrenches, levelling blocks, chocks, water jugs, blue tank, X-chocks, stabilizer bars, future mods to store sewer hose, bins to organize "stuff", the Coleman stove, lantern, firewood, charcoal, and the list goes on and on......

I think you're headed in the right direction with your calculations, fine tuning them will hopefully give you some indication of what to expect. Remember that as your family grows, the weight will also increase. Pre-teens are "social beings" and trying to "rip them away from their friends" makes for a stressful camping weekend. While they are content with "tigger and a favorite blanket" as toddlers and very young children, their requirements to be happy become much more sophisticated as they grow older. That means weight, payload and dad's "sanity" will also become "heavier"

Good Luck !!!