Is there a problem with setting VTF this way?

I was wondering if anyone else has tried setting their tracking force this way. I have a very accurate laboratory beam balance scale with which I weighed out a blob of blue tack weighing 1.7 grams. I attached this on top of the headshell over the stylus contact point. I then adjusted the VTF until the tonearm was balanced, horizontally level in equilibrium. I removed the blue tack, VTF should be set at 1.7 grams. Is there a problem with this method I haven't thought of?
Yes, you be tracking at NEGATIVE 1.7 grams (tone arm will rise to its upper limit stop, in actuality).
Your idea is fine although you should place the blue tack on the tonearm counterweight. Then balance the tonearm. Removing the blue tack would then give you the 1.7 grams.
Humm, I've not kept up with my physics, but I don't think 1.7 grams placed on either end of a non-symetric fulcrum will give you 1.7 grams of down force at the stylus. I think a down-force gauge used at the stylus tip is the only quick and accurate means of verifying downforce. Unless, of course, you are a mathemetician or physicist!

The scale on you counterweight is calibrated specifically fot the physical properties of your tonearm, I would guess.

My best guess.......

Reading the comments in this post prompted me to do an experiment. I wanted to see how extra weight affected a tonearm.

Several months ago I formed a ball of Fun Tack by pressing tiny bits into a clump until I formed a perfect counterbalance for my Walker tonearm. The purpose being to perfectly balance the tonearm parallel (and above) the platter. Balanced this way, the suspension adjustment knob may be turned to achieve zero anti-skate.

I just weighed this successfully formed Fun Tack ball with my Winds track force gauge (100 ths of a gram model) with a reading of 3.94 grams.

Without the Fun Tack my Koetsu measures a tracking force of 1.92 grams at stylus tip with that same gauge.

Unknown if results with a Walker applies other tables, but on the surface, TIC's guess appears to be correct.
Knock me over with a feather again. I figured the arm to be a balance beam using the blue tack on the counterweight. If I'm reading Alberts post correctly then there is a 1/10 gram discrepency.
Perhaps the following quote might help:

"...For since under the impulse of the same weight the greater radius from the centre moves the more rapidly, and there are three elements in the lever, the fulcrum, ... and the two weights, the one which causes the movement, and the one that is moved : now the ratio of the weight moved to the weight moving it is the inverse ratio of the distances from the centre..."

from "The Mechanica", a script written by the Paripatetic School somtime between Aristotle's death in 322BC and prior to Archimedes' birth in 287BC.

I am sure Archimedes would see no problem with Photon46's concept if carefully implemented.