Finished phase one ground tests (limited range use, but engine running, all settings) with the A123 feeding a MPI 5.4v, 10A regulator.
All worked fine.
As expected, total milliamp draw from the A123 was as much as anticipated, indicating the reported current draw of the RC-EXL ignition is about as stated.

There were no issues, nothing to report, really. Solid, reliable performance and nothing visible in radio-land because of it.

Way too hot/windy for me to do more, so I just continued breaking the engine in.

Phase two will be at the field, ground tests, bind button depressed to find engine on/off limits to range, all attitudes of airplane. If all's well there, then there is only the airborne test remaining.