> 	col := {337 at 314 .  327 at 274 . 320 at 237}.
> 	(2 * 400 at 0) - col
> 	-> this fails :(

I don't have a real understanding of what you are doing, but this version
seems to give the expexted result: #(463 at 314 473 at 274 480 at 237)

col := {337 at 314. 327 at 274. 320 at 237}.

(2 * 400 at 0) - col * (1 at -1)


Hope this helps,

German Morales