Hi Deker,
I went for the second lightest spring and the thickest tube, red I think, can't remember, but it was defo the thickest. It stills has a little creep, but it's far better than stock.
The spring seems safe too. Went through the whole smacking the gun with a rubber mallet shenanigans and it held true. Over 2000 rounds later and not one nasty incident.
I was thinking about wrapping a little tin foil around the tube to eradicate all creep. It's more than good enough for 1/2" groups at 50yds though, and as I only use it for rabbits not paper, I have left it in it's apparently