So I finally got around to measuring the shell fit of my size 25.5 Radiums. With the foot weighted I seem to have 15 mm behind the heel when the toes are lightly touching, and perhaps 1-2 mm on either side. With the foot unweighted there is several mm more space on the sides. So for a touring fit the size sounds right to me.
When I try to buckle down the instep buckle (1) to the max tight setting while still not wearing liners, I have several cm free space above the foot. I can easily pull my foot out of the shell with this one buckle closed. This is with one very thin footboard in the shell. Is this normal? The problem I have when skiing with the stock Garmont liner is that the boot is too roomy over my foot, even though I have a thin footboard, a custom footbed in the liner, and crank down the two lower buckles all the way. I wear two pairs of thin socks, since one pair leaves me swimming.
I have also used the boots with Zipfit touring liners. In this case the foot is held nicely in place without tightening the buckles all the way. Also, they do not pack out during the day. The problem with these liners is that the heel pocket is so narrow that it causes massive blistering on touring. They are also a bit cold, but that is the case with the Garmont liners as well.
(1) I don't know if that is the right name, but I am referring to buckle two when starting count at the foremost buckle on my four buckle boot.