For those that have built their own trailers with leaf springs, please chime in and verify my estimates. What else should I consider when choosing leaf springs?
I'm going to build my own trailer basically following these plans (more or less)....

https://myhub.autodesk360.com/ue29cb58f/g/shares/SHabee1QT1a327cf2b...

Trailer will be constructed from 2x3x1/8" wall tubing with leaf spring suspension and 13" tires.

Weight estimates:
17' Don Hill Flyfisher= 350lbs
Trailer sprung weight (not including axle, wheels, springs) = 300lbs
Misc (oars, cooler/ice, other stuff) = 100lbs
Total Sprung Weight = 750 lbs

A *very* loose "rule of thumb" that I can gleam from reading on how to spec leaf springs is to pick a total axle rating that is double the sprung weight, in my case 750 X 2 = 1500lbs....basically choose qty two 750lbs rated leaf springs. Does that seem reasonable for a 17' wooden drift boat?  My concern is ending up with springs that are too stiff resulting in a bouncy ride.