While browsing ebay a while back I came across an ebay seller selling the LM2596-ADJ switching regulator with all external componets (the caps, diode, inductor, trimmer, etc) already soldered with the regulator to a pcb. AND for only $7.50!! It's absolutely a breeze to work with. Only need to connect Vout to the atty connector (pos Vout to to atty inner and neg Vout to atty outer) and Vin (pos Vin to one leg of the switch and neg Vin to the neg connector of the batt) and the other leg of the switch to the pos pole of the batt. Zip zip lickity split and it's done. The seller also includes 2 connection cables (one for Vout and one for Vin). DC-DC Converter Board regulator In:3-30V Out:1.3-18V - eBay (item 300459975900 end time Sep-24-10 23:28:48 PDT) Here's what it looks like: I used a 4x2x1 enclosure (Hammond 1591ABU). I cut 2, 18650 batt holders in half, trimmed them to size, then glued the halves back together to fit the 16340 batts. Checking voltages. YAY - it works!! All done. Size comparison with a 3AA batt box. And of course, my helper had to make an appearance.