RE: 4.8v to 6.0v
A few servos that are not spec'd by the manufacturer for 6 volts.
Hitec:[ul][*] HS-45HB[*] HS-50
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Futaba:[ul][*] S9206[*] S3115[*] S3110[*] S3111[*] S3104[*] S9102[*] S136G[*] S9151[*] S.... the list goes on
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Will they work if used? Perhaps, but is it worth burning out a servo and worse, losing a plane? The good news is most servos are ok on 6 volts. The simple solution is to just confirm that the ones being used are ok for 6 volts.