I'm with ComfortZone on this I like a lot of tongue weight. You can have to much tongue weight, you just have to balance it. To much in a small vehicle and it starts to effect the steering in the sense your lifting the front off the ground. I Pull about 8000lbs and have about 1500lbs of tongue weight thats about 18-19%. The trailer is tandem axle and tracks straight and true. I also think that hitch height makes a difference when you have a tandem axle trailer. The trailer should sit totally level when all pinned up. I don't know how many times I see guys with the hitch way up in the air and the front tires of the trailer almost not touching the ground.
I found this to help people figure out there tongue weight
Commercial Scale
Another way to determine your trailer's tongue weight (and get your vehicle and trailer weights) is to take the trailer with your tow vehicle to a scale at a truck stop, quarry or material supply centre. For a small fee, you can weigh your tow vehicle and trailer there.
A. Determine Weight of Vehicle with Tongue Weight
Your vehicle and trailer must be fully loaded and fueled just as they will be when you are leaving for a trip. First, drive on to the scale with all 4 wheels of the truck and record the weight of the truck with the trailer attached.
B. Determine Weight of Vehicle without Tongue Weight
Next, unhook the trailer and jack up the trailer tongue so there is no weight on the hitch ball. Make sure that the trailer jack is not on the scale. Record the weight of only the truck on the scale. This is your gross vehicle weight (GVW). Now, subtract the GVW from the weight of the truck with the trailer attached. This will give you the tongue weight of your trailer.
A - B = Tongue Weight
Determine Tongue Weight for Weight Distribution System
If you want to use a weight distribution system, remember to include the weight of any gear you might load behind the rear axle of the tow vehicle. You should add the weight of this gear to your tongue weight to select a weight distribution system of the proper size. To get the weight of the gear behind the rear axle, weigh your vehicle with this gear and without. Then subtract the weight without the gear from the weight with the gear. This difference is the weight of your gear. In the formula below, C represents the weight of your gear. A represents the weight of your tow vehicle including the tongue weight. B represents the weight of your tow vehicle without the tongue weight.
A good time to get this weight is when you are determining your tongue weight as described in step B, above. You can get the weight of your gear while you are weighing your tow vehicle.
Weight of Vehicle with Gear Behind Rear Axle - Weight of Vehicle without Gear Behind Rear Axle = C (Weight of Your Gear)
A - B + C = Tongue Weight for Weight Distribution System
Determine Additional Weights
Weight of Your Trailer
While you are at the scale you can also make sure that your towing setup is within the rated capacity of your tow vehicle. To do this, you need to get the weight of your trailer. To weigh your trailer, pull it with your tow vehicle onto the scale so you can weigh them together. This weight is your Gross Combined Vehicle Weight (GCVW). You can get the weight of your trailer (Gross Trailer Weight - GTW) by subtracting the weight of your tow vehicle alone (GVW (Step B, above)) from the weight of your tow vehicle and trailer combined (GCVW). Then check your owner's manual or with your dealer to determine if the weight of your trailer is within the towing capacity of your tow vehicle.
GCVW - GVW = GTW
