Is there a way to reference the location where a projectile has made impact (for example determining where a summon spell hits in order to place the new summon) within Papyrus. I wanted to cannabalise the scripts for the existing summon spells but can't access them in the magic script effects menu.

I think you can do this by adding an explosion and adding a scripted "Placed Item" (I think that's what it's called) to the explosion.

Cipscis

If it's in a dungeon, and you have a specific object in mind, you could put invisible pressure plates everywhere, not call the animations to avoid the clanking, but have them trigger when that particular object ID enters their trigger area (and enlarge the trigger area to about the size of the summon, and overlap them a bit)

The summon spells use a Delivery: Target Location thing that I guess you could use if your projectile came from a spell. If you are thinking about arrows or stuff like that, I remember in Thieves Arsenal for Oblivion scruggs added vine arrows that "from what I remember" worked like that. If nothing else, you could check what he did back there and try to adapt it...

Spells by default get applied to a projectile... So just swap the projectile with your own.

You trying to make a "Blink" spell? I'd like that.