Just thought I would give an update from a question I had some time ago. What happened was I bought some Montec SC 100 grain broadheads and the base, on this particular model "CS", is very small compared to the diameter of the insert. So when its installed then it would leave quite a noticeable flat edge exposed that I don't believe most people would accept as being ok at all. Well I found what I feel is an acceptable solution to this problem and finally bought a camera that can take half decent pictures. So just wanted to let someone know so it might help them if they came across this issue and didn't know a fix for it. Hope this might help someone.
The product is called Universal Broadhead Adapter Ring and it does not take all of the flat edge away but I would guess that it eliminates a good 90 to 95% of it. It certainly makes the transition much smoother. The wide part of the adapter ring is the exact same diameter as the brass insert and the smallest part of the ring is almost the same as the base of this particular broadhead.
You should be able to see it installed between the head and the insert in the pictures...
