INTP:
I have a bias against boosting voltage and losing available current. It's not a good bias to have, because there are obviously times when losing current is acceptable, but it just means I don't have boost modules on hand to tinker with.
The 6V rechargeable SLA sits at about 6.5-6.7, so an LDO reg would work considering its large capacity making the voltage not drop super quickly with meager power demands.
So you suggest not using a booster.
I believe that using 2 of these: Pololu 5V Step-Up/Step-Down Voltage Regulator S7V7F5
1 for supplying the Arduino MEGA 2560 through USB ( I have done this before)
and 1 for supplying the rest of the sensors circuit
is ok, right?