good question - it depends. When I started out, I never did. I went through about a dozen different epoxies since I started this, and they all were great when gluing wood to wood, stabilized or not. So, in that case I don't use dovetails because the bond is so strong that I have no concerns about them.
But I always had problems when using metal spacers: When sanding the glued handles, the thin metal spacers would heat up in seconds, and the epoxy bond would come apart because most are only heat stable up to about 200F. Because of that, I have started using not dovetails but little dowels inside the handles when I use metal spacers, and occasionally also with other spacers that can be a bit brittle. I haven't gotten around to drawing it up, but basically, I predrill the handle piece with a thinner drill, 3 holes next to each other then turn into a slot for the tang. Then I drill a wider hole 1/" - 1/2" into the handle and into the ferrule and connect them with a softwood dowel. If I use a spacer, I drill it with the same diameter and just slip it over the dowel. All this does take quite a bit more time (which is why I have slightly raised the prices for handles with metal pieces), but it is very stable. I have tried to intentionally break one of those handles and couldn't do it with reasonable force.
I am not sure that I get the question. One of the differences between Marko's handles and mine is that - like in your picture - you can see the horn as a ring around the hardwood with the tang slot in Marko's design. In my handles you will only see horn and the tang slot, the dowel is inside and hidden. Marko's style looks more traditional, and he can do that because he matches them directly to the knives. Since I do this only when I find the time, I feel uncomfortable having peoples' knives around for too long, especially if they make their living with them. I make mine as I do because that way the tang slots can be matched to different knives later, depending on what someone buys it for. Not sure if that answers your question...
Yes thank you Stefan .
the horn is touching the tang so no need to have a said wood there to match the handle there.
Nice i like your idea Ive had my share of problems with handles and metal spacers
so any info i can gather along the is most helpful thanks.
Now maybe I will give it another shot .
(sorry i don't have a picture of a handle of yours in that position)