[kalev]

Can't comment on Stellar specifically, but unless it's a total freak year, there should be loads of snow mid-end of March.

Kaslo is an awesome little place (not far from where I live), with epic terrain / mountains. I'm guessing only 2 things could happen:

1. You get an unusually warm / sunny spring and south facing slopes could be sun affected, or lower slopes have poor snow. But given you're in a helicopter, they can take you to north facing / high elevation slopes that still have good snow
2. It's snowing too much, so the heli can't access high alpine terrain and you'll have to ride pow in the trees

Sounds like a no-brainer. Make sure you report back if you're able to go!