Happy to help, I was considering this for a long time but thankfully saw the light.
Another thing, don't bother with a bloody trigger spring!
Not sure if you have tried winding the factory screw out a little bit by bit and checking, was able to get very good breaks on both of my t3x and t1x.
The whole trigger spring thing comes down to the fact that US (and hence North American) guns need to pass the SAAMI standards which includes a drop test to see if the trigger goes off. As a result the '3lb standard' applies and most US made factory guns will have a heavier trigger when compared to European makes, hence why the US aftermarket trigger market is huge.
There is a theory (no one has confirmed it, but it floats about on forums like SnipersHide, don't want to mis-inform) that Tikka and Sako ship North American firearms with lighter springs. Not sure if they can get set triggers either (no loss there!). But anyway, as a result, the 'light spring kits' have become a huge aftermarket thing. If you lose the spring plunger when changing springs or install it the wrong way round you are in for a costly replacement.
If you really are set on changing the spring, you could measure the dimensions yourself and look for a replacement with a thinner gauge or simply less compression. There are guys who are charging £20 for a £2 or less part. Another technique is to 'collapse' a few coils of the standard spring by heating them, thus giving you a shorter spring.
Please take all of the above purely as information and not advice. If I am giving any advice, it is to leave it alone!
Cheers.