Seriously? This is a far cry from "they really recommend a 1s." If there is something else from MW to support your statement, may I have a citation?
From the RRC3 quick start guide:
The RRC3 is designed to be powered by a standard 9‐volt alkaline. You can use any battery in the 3.7 ‐ 10 volt range, but there are other considerations when using these alternate battery types.
From the RRC3 manual:
The RRC3 is designed to be operated with a standard 9‐volt alkaline battery. Standard 9V alkalines are an optimal choice, providing an inexpensive and widely available battery type with secure snap connectors. Always purchase and use premium alkaline batteries. Other battery types can be used, including NiCd, NiMH, LiPo, or other battery chemistries. Your battery choice must source and maintain an absolute minimum of 3.5 volts, and also be limited to a maximum of 10 volts.
From the RRC2+ manual:
The RRC2+ is designed to be powered by a standard 9-volt alkaline battery. You can use any battery within 3.7V to 10V, but there are other considerations when using these alternate battery types.
On another note. I have been using MW for 13 years and have maybe a dozen or so. If weight and size are not an issue, I use a 9V. Otherwise, I typically use a 120 or 180 2s LiPo. They all work well. This is my 38mm Nike-Apache bay:
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