I suggest you look at the Inland DC-DC Voltage Step Down switching converter module. Input is 3 - 40 VDC, output current up to 3A, precision Vout adjustment via multi-turn pot. Micro Center has these for near $7, their designation is K98R.
I think these may go into continuous conduction so voltage drop can be minimal (module is TI LM2596 switcher based).
I guess it depends on what your load is going to be and how much room you have for the unit. We have been using these for general purpose especially for higher current applications such as solar panel input. They will let you use 40 volt, 150 watt, 7 amp (x2) panels input. They are adjustable down to 1.2 volts or up to 36 volts at up to 20 amp 300 watt output. Of course they convert the extra voltage input not needed to additional current output.
Both voltage and current output are adjustable and they are 95% efficient especially if you don’t need to throttle down the output current for any real reason. And if room is not a problem they are only 2”x 2”x 1”. These we have tested extensively and they work well for about everything. Custom LED displays on cars is the most common use. $20 for two.
Technical Specifications:
Input Voltage: 6V to 40V DC (10V to 40V is suggested)
Output Voltage: 1.2V to 36V DC
Output Current: 20A (max.), 15A (suggested)
Efficiency: 95% (24V to 12V, 20A)
Output Ripple: less than 50mV
Wiring Method: Terminal
Short Circuit Protection: Self-recovery (cannot short circuit for long time)
Size:60×53×27mm / 2.36×2.08×1.06 inch(L * W * H)
Pins Description:
VO+: Output positive
VO-: Output negative
+IN: Input positive
-IN: Input negative
CV: Output voltage adjustment
CC: Output current adjustment
When input and output is common grounded, no-load CV output constant voltage,CC output constant current