While my experience with the Tadpolly is globally recognized, please don't confuse my response as an Official Guideline or recommendation from Heddon.

Starting with 15 feet of line use the following equation:
A = Current Speed of the Water measured in Knots over Ground
B = Y Axis Degrees of Rod Holder with 0 degrees being water level
C = Rod Length
D = Number of Feet of Line from Rod Tip to Tadpolly Head
E = Current Water Temp in Celsius
F = Water Salinity measured in PPT
G = Depth in Feet

G = (D-(C*(B/100)))*((A-1.3)*.71)-((E*.001)+(F*.0128))

Important things to note:
1. This formula will only work for a clatter tad. The bouancy of the rattle does impact the depth factor used.
2. Because there are no ISO Standards for Rod Weight, Action and Flexibility we are only able to support the accuracy of this based on the use with a Lamiglass 8' 6" 12-25lb (Fast Action Heavy Power - Kenai Special)
3. If G is a negative number this does not mean the tadpolly is in the air, it would indicate floating on the surface. Apart from casting and bird strikes it is very rare for these lures to achieve gravitational defiance.

I hope this helps those looking for more accurate fishing tactics.