I ended up cutting the end off a piece of 1/2"aluminum rod at about a 10 degree angle. On the shallow side it's maybe 3/16" thick. Then I drilled a 1/8" hole, centered on and perpendicular to the angled face so it comes out near the edge of the non-angled face.
I pre-bent the mandrel of the rivet, slid the tool over the mandrel, and insert the business end into the hope. That have me plenty of clearance.
Thanks for the help, boys.
RV-8 Empennage started