Clamping scarf joint in chestnut keel?

[Wrothgar]

So I milled the keel before scarfing it to length....on a chestnut with a square /trapezoidal shaped keel. The sides are tapered...and this is making clamping the scarf joint tricky. Any suggestions?

 

[MGC]

It's cheating but what I do is cut the head off of a very small brad and chuck it in my drill. I run it in from the back side of the joint (so that it or the hole it makes cannot be seen). The brad keeps everything from sliding away when you clamp it. I hope that makes sense? Think of how a toothpick keeps the tomato from sliding away in your BLT...same idea.
After the joint is cure you can either pull it back out or trim it flush.

 

[Wrothgar]

I did something like that....