a little while ago i got a new made spring off ian, having finally gotten around to fitting it yesterday i thought i would report on the difference, i measured two figures, one was ground clearence and the other was how much the trail was brought in before and after the spring was fitted, my old and original spring measures just under 9 inches uncompressed, the figure it should be 'new' is ten inches uncompressed, after fitting the new spring, ground clearence was increased by 1 1/4 inches and the trail was brought in by just over an inch!
having gone out and run the bike through its paces today at different speeds and over different terrains there is an appreciable difference with firmer riding, better cornering and handling at higher speeds(in the 50s mph) and also a higher feel to the riding position,it handles better and reacts to bumps, potholes and rougher terrain with much more vigour and suspension action.
having looked at the sudden flow of springs onto the market i thought i would also mention something to think about, the spring is what is termed an essential component, if it goes at speed it can kill, so knowing ian and that it was manufactured to the correct specification by a company with good knowledge of spring production and treatment i was confident in it for safety,
however i would not be so trusting of an unknown spring, apart from quality of metals, inclusions and bubbling, as well as proper heat treatment there is also the question of proper fit on the scrolls, when looking at a spring, ask yourself, do you trust your life to this component, and do you have the confidence it was made to a high standard.
anyways there is an appreciable difference in handling after fitting the new spring,and checking this component can let you improve handling. just my thoughts after testing.
Interesting feedback Jon (literally!). I'm looking forward to fitting refurbished forks and a new spring to my own M20..I know my saggy original spring hasn't been replaced in the last 26 years and the fork action is all over the place.
Ron Pier has taken a while to get used to the altered 'feel' of his bike after a front end overhaul, which also included a new spring. Reading your comments on the revised geometry of the bike, especially the trail measurement, I'm not surprised it feels different....Ian
Yep the new spring and fork bushes certainly iron out some of the jarring on rough roads that I had become used too. The handling feels different with the bike more prone to drop into corners at low speed. Something I will hopefully be getting more used to in the sunshine this weekend. 
Ron
email (option): ronpier@talk21.com
I have seen the springs Jon is referring to on e bay...available for 16Hs and M20s..I assume these are a spin off from the Indian manufactured girder forks.
I haven't spoken to anyone who has tried one yet.
I agree with Jon...you have to be careful with these 'stressed' components. It appears the Indians are increasingly moving into these types of parts, frames,forks, wheel hubs etc...I think a used original would probably be a better and safer option...Ian
Steady lads, if your front fork spring should break it will not immediately bounce you over the parapet of a bridge into a 200 foot deep ravine where your skeleton will lay undiscovered next to the rusting remains of your favourite bike for the next millennia.
Apparently a broken spring was a fairly common occurrence especially during military service where a certain amount of non road work was done.
This is from an October 1943 R.A.M.T.S book.
email (option): robmiller11@yahoo.co.uk