I "did the dowel trick" over the weekend -- needed to make 2 dowels, they occupy the two battery slots closest to the back of the hd-p2 (which was surprising to me and required me to remove the battery holder to understand/confirm). Also had an opportunity to do some run time testing.
I found that I was able to get close to identical run times (just over 10 hours with phantom on powering a Studio Projects LSD2 and recording at 24/96 with the HDP2's lights all on) using either a) a 12 volt 5000mah NiMh battery pack running through the HDP2's external power adaptor or b) a 9 volt 5,500mah LiIon dvd battery via the "dowel trick" -- using the dvd battery, the hdp2 battery meter showed about 1/3 full from the start (which makes sense given that the hdp2 is expecting 12 volts (8x1.5 volt aa batteries) through its internal battery connector.
Right now I'm running both of the above batteries simultaneously to confirm that it'll fill up the 32gb cf card (15+ hours at 24/96) without any intervention while powering the LSD2. Once that's done, I'm set for telluride.