Some Cursory thoughts

The S2f for gold is variable and not strictly decreasing (quite static over time) so I don’t know how good of models can be built on top of it.  

Also the s2f of gold is a function of price/demand so it further complicates things (Low one year, higher the next, then back)- not so with BTC. 

 Strictly increasing* 

 Does SF2 work for litecoin or bitcoin cash? 

 Supply based models don’t account for demand characteristics, and demand is based on if the coin is a good money. 

 So what good is a model that doesn’t account for half of what makes up the price?