I wish I were nearby, this is the only runner style I do not have for the conditions we often see. I have a set of the first style from a swap meet years ago, but they are slow until the slush gets deep. Everyone quits as these runners come into their own. I have seen conditions where these runners were the best maybe five times in the last twenty years. But when they are best, they are very best, and you cannot sail fast (or sometimes even move) without them.
There are two styles. One has a long gentle lead-in and a profile much like the alligator-nosed sarns. This profile is best for deep slush and salt water slush, when heavy air is needed to move. Mike O'Brian won the worlds in the Ancient Days with a set of these in (I believe) Russia. In the US, we see conditions best suited to these runners and decide it is not good enough to sail. In Europe, they race in these conditions.
The style best for the conditions we have here, according to John Dennis, is maximum length, 100 degree edge (ground or bent into the angle), with the same profile as other runners (18 inches or 0.008 flat). Many with the same profile and 90 degrees are around as they are good and far easier to build. This runner is fast early when the ice is tight and bumpy, and stays on top of softening slush. It also efficiently gets through deeper slush. Very sharp edge is not required or desired in soft ice. Wet and dry sandpaper is used to touch up and polish the soft stainless. Bob Rast made a set with cheap carbon steel angle from Ace Hardware, and they worked great, except he has to keep them oiled when stored.
The runner can be very light as the angle spreads the side forces over a large area. Wood body, threaded stock welded to the inside of the angle inserted into holes in the body seems to work.
To confirm or get the word from the horse's mouth, try an inquiry on the MN site:
www.iceboating.orgGood luck! Build extras, they will sell well.