I think you made the right choice, most people I have talked to who bag them were confused with the differences between the old eutectic (sp) types and the newer but still old element chescolds or just couldn't use them properly or any of the above and probably some more even

as mine is not a special case but has never let food thaw we didn't want thawed -ever!
The Chescolds with the element will keep meat frozen at 35-40 deg daytime in the back of the old patrol (no aircon) on 12v on a 5 day road trip to the tropics, the thermometer we had was set to warn us at -4deg and it never went off, night time was on gas and around 28-32deg.
A couple of hints on how to deal with them, use dedicated 12v to the freezer of a gauge large enough to handle the amps. This will see sub 0 temps when traveling in 35-38 deg heat.
No need to rev it up before the trip like the finches etc just use a frozen 2L bottle of water placed in it with the warm drinks at the start of the trip to kick start it or just the frozen meat and refrigerator stuff as per the Engel.
When packing as the element is at the top if you pile the meat in to create a cap of food the lower levels may start to thaw over time on 12v and might on gas at 35deg also. Pack so that there are gaps to the bottom to allow the cold air down to the lower areas.
Also consider a partition of plastic on the far side of the case to the element that divides the space into two sections, works real well to stop the milk, drinks, cheese, marg etc from freezing and turbos the element side somewhat as a bonus, don't forget to pack so the cold air can reach at least a portion of any food that needs freezing.
At 27 deg I have measured - 17 deg in ours.
Another thing, don't treat them like the drinks fridge at home, for stuff needed regular keep an esky with ice made in the chescold overnight in 2L bottles. Works a treat if you have kids or a few drunks in camp

.
My Engel is great for road trips but a royal Pita on those lovely easygoing extended base camp type trips we infrequently (now

) enjoy.
cheers fnq
*JUST LUV IT* 96 GQ LWB TD4.2, Cav, Kings, Dobinsons, Motorguard, Enginesaver, 400 pro, Cooper ST's (rolls eyes), fleetguard oil filters, Delo 400 engine oil, Delo ESI gearbox oil and an RTC.