I'm sorry Bdomini, but unless that 'someone' has
EXACTLY the same trailer as you with the same tires running at
EXACTLY the same pressure & with
EXACTLY the same pre-load on the trailer bearings as well as having an 'A' arm & hitch that's
EXACTLY the same dimensions as yours, plus the tub vehicle has
EXACTLY the same height tow ball/tongue and
EXACTLY the same weight Spyder that is
EXACTLY the same dimensions & weight balance as yours, then their experience is at best only going to be a
very rough guide for your Spyder placement; and a difference in any of those &/or a difference of just a few inches in placement fore & aft or as little as just a few lbs in weight balance positioned over the trailer axle could make a big difference in the down-load on the towball/tongue.

pps:
So as has already been mentioned, if you are concerned, & you probably should be if you can't reasonably well judge that 10-15% of your trailer total loaded weight (can anyone really??) then you probably should check the download weight, cos getting that wrong can badly impact on how well the trailer tows, & getting it
really wrong can be pretty bad news for both the tug vehicle AND the trailer & load... and possibly also bad news for some of the vehicles &/or people around you when it all goes pear shaped!! :yikes:
Getting the hitch download right isn't all that hard, try loading the trailer & then putting the hitch end of the drawbar on your bathroom scales & moving the Spyder back & forth until the balance/download is right - most bathroom scales read up to 280 or so lbs don't they?? Besides, very few 'non specialist' tow hitches that might be mounted on the back of your tug will really be up to carrying much more than about 300lbs download anyway.... :thumbup: