To use doubles while traveling you have 4 options:
1. bring your own doubles
2. bring your own manifold and bands and find a shop that will allow you to rent their tanks, drain them, de-valve them and band them with your bands and manifold for the duration of the trip. (not likely to happen)
3. Rent manifolded doubles at your destination. (also not very likely)
4. Use a set of travel bands as independent doubles where you have a reg on each post but no manifold.
# 4 works pretty well, you just have to manage te gas properly to retain a fully redundant gas suply throughout the dive. You use 1/3rd of the first tank, switch to the second tank, use 2/3rds of it and then switch back to the first tank to use the 2nd third of it - leaving the last 1/3rd in each tank as a reserve - assuming you are doing overhead or deco diving.
You can get a set of travel bands here:
Aqua Explorer Ultimate Double Tank Bands from LeisurePro.com
My only complaint about these bands is that in very cold weather the plastic cam buckles are prone to breakage so I replaced them with metal cam buckles on mine since I seem to find my self diving in very cold water and even colder weather from time to time.
Diving doubles is not nearly as hard as people make it sound. Unless you have a set of enormously negatively bouyant doubles they are actually more stable than a single tank - provided you use a backplate that is able to stabilize them. And with proper streamlining they really have no more drag that the average open water diver's single tank and jacket style BC with hoses flapping in the breeze.
The caution with doubles is that they have about twice as much gas as a single tank and as such you have more than enough gas to get into serious deco trouble. You also have about twice the weight change during the dive as instead of being 4-5 lbs heavy at the start of the dive, you are 8 to 10 lbs heavy with the extra air in the tanks. So your bouyancy control needs to be good and you do not want to be over weighted. You need to be sure you are properly weighted and choose your tanks carefully so you are not overly negative in the event your wing fails and you lose bouyancy. AL80's make good starter doubles in that regard and they work well with a wet suit where you do not have a dry suit available for redundant bouyancy.
In short, the key to diving doubles sucessfully is to use a backplate and wing and get a little help in configuring everything properly - that can be the complicated part. Once that is done right, the in water portion is a breeze.
