Ben and I finally got to try this combination.
Since there were only two of us with but a few hours, we played the short game. 15 turns, all heirs on the island, and a nasty optional gales at sea card to sink anyone sunbathing offshore.
We each picked a player-noble. Ben took Fitzalan and I took Pole. We then each got 17 cards, with me getting the far better offices (Marshal and Constable of the Tower of London).
After we grabbed all the heirs but poor Richard of Gloucester way down south in Plymouth, Ben's two key nobles got called north to deal with Mel Gibson's Scottish raid. We were playing a variant where two event cards are dealt, then movement is done randomly, after which all sieges, combats, coronations, etc. are done, then finally the power-up card. It's a lot of fun, because if you go early, you can scoot from trouble or launch an opportune attack. If you go late, you can swoop into an already looming battle to swing it one way or the other.
In our situation, If Ben went first, he could regroup, but the dice said I got to move first, so I attacked his stack with Richard of York (already crowned).
We then went to the Battlelore game. I had all the advantages of more units (20-18), more nobles (hit on lore if they were present), and 3 war council members to Ben's 0 (based on bishop cards), but his well played counterattacks resulted in a tight battle with a 9-7 margin.
We called the Kingmaker game at that point. I had based my unit assignment system on more players, so we each ended up with a lot of crown cards, which pretty much emptied my box and used a lot of the supplemental units to boot. With 3-6 playing, I don't think this would be as much of a problem. We got to use the mounted knights, the hobgoblin spears, ostrich and hyena riders, horn blowers, and other nonsense. Still, I might have to consider buying another battlelore set for Kingmaker parts down the road.
So I've got some more adjusting to do on the conversion system, but overall the combination works pretty well.
A great playtest session, and I'm very appreciative of Ben donating his time. We probably should have just played CnC Ancients, which is a better game with less bother. Unfortunately, I don't have a good campaign tie-in for it. And I do enjoy medieval history above all other subjects, so will continue to work with Battlelore as a vehicle for Kingmaker battles.