In the mean time I found a better way for contructing the frogs, shown here. This give me enough confidence to try for my ultimate goal: replacing the Peco single slip switch with a better looking turnout. I went for broke and tried building a #6 double slip switch. It turnout out pretty good looking, but again I had gauge problems at the knees of the wing rails. But the big problem was with the throw bar. Two pairs of points attached to each throwbar made them impossible to move, there was no way a tortoise switch machine was going to throw this even with my new linkage (shown here).

So in my second attempt at a slip switch I went with a single slip shown here. I got the gauge pretty good throughout and with just one pair of points on each throw bar I was able to get the tortoise to move them, though these throw bars are significantly stiffer than a regular turnout since the point rails are much shorter.