I have never had a carbon steel spring that snapped or that gave for too much softness. I temper thoroughly the spring with the blade (380-420 °C depending on the steel), and then draw the spring to light blue only in the flex portion, including the first hole, with a soft propane flame, taking time and care. I leave the walk of the spring (the part that engages the tang) hard as much or only slightly softer than the tang.
My concern would be if the oven spring tempering would lead to gall the "walk" spring portion with the much harder tang in the long run.
For a spring the important and foremost thing is an even lath structure and a through tempering, a couple of hrc point less would add more toughness for the ease of mind, hence the drawing to blue, but if the microstructure is sound, a well designed slippy spring could be used even in high hardness range. I tested springs for destruction and trust me....those snapped springs you hear about in slipjoint horror stories most likely had troubles before even going into tempering!
I consider this subject (in theory) a point for carbon steels over the stainless, for this application. I wouldn't selectively temper stainless as easily as the carbon steels.
1080, btw goes for a very nice spring.
If you go for the oven tempering please tell me if you have galling (sp. galding?) or not...oiling the joint of course