@mesrins Thanks for your reply. Just to button this up, I settled on a high-deductible Medigap Plan G. For the lower premium I have to meet a $2,490 deductible. However, amortized over the cost of a full year it's about the same as paying a full Plan G rate.
The decision was guided by 1) I'm in good health, 2) constant headaches with private health insurance plans over the years with regards to their particular medical necessity guidance, 3) narrow networks in MA plans and portability of Med Supp plans, and 4) just plain incompetence by insurance companies in claims and payments causing excessive and needless management on my part.
Of course, I also signed up for a Part D plan. Although I don't take any meds now, one has to sign up to avoid a penalty. I took the least expensive one in my area.