To control the overflow after parking for cruise night I would just use a plastic commuter drink cup that I placed in front of the radiator support. Was removeable within seconds. To get a little better heat removal in summer you can run Water Water with straight demineralized water or with a glycol/water mix of around 10/90 or 20/80. When I ran the 160 deg stat in the car during colder weather I'd just block off part of the radiator core with a piece of cardboard to optimize running temp, and allow a quicker heat up. On winter maintenance runs in 25 deg weather I'd have about 80% of the core covered. Simpler than swapping stats.

RR69s