Double 72's are not a lot of gas, so it does make some sense to get larger tanks to ensure your buddies can actually take advantage of their larger tanks.
Still, it is worth knowing how to gas match different cylinders because you will encounter it a lot. Basically, figure everyone's turn pressure based on the cubic feet used by the smallest set of tanks. This is important as those tanks potentially have YOUR reserve gas, not the guy with the small tanks.
You can do it pretty quickly by using the tank factors for the tanks involved (rated capacity divided by fill pressure at rated capacity times 100, which will give you the number of cubic feet per 100 psi).
For example, if the plan is to turn on thirds,
1. The diver with X7-100's pumped to 3500 will round down to 3300 (the nearest pressure easily divisible by 3) then divide by three to get 1100 psi for the first third - a turn pressure of 2400 psi. (3500-1100=2400)
2. His tank factor is 5.8 (100/3442 = 2.9 but times 2 since he has doubles = 5.8). So 11 times 5.8 is 63.8 cu ft used in that third.
3. The diver with 130's pumped to 3500 would turn after using the same cu ft, not the same psi, to ensure the "thirds" are equal.
4. The tank factor for the 130's is 7.5 (130/3442*100*2 = 7.5)
5. 63.8/7.5= 8.5 or 850 psi. So the turn pressure would be 3500-850= 2650 psi
With a little practice you can do the math in your head. In this case the guys with the 130's are giving up about 250 psi in the turn pressure. That is in the end not all that horrible as they are only giving up about 18 cu ft of gas for the penetration portion of the dive.
If you figure it all with 72's (TF= 5.8 for steel 72's or 4.7 for 3000 psi Faber 72's) you end up with only 47 cu ft per third and the guys with 130's are turning after only 625 psi and are giving up giving up 475 psi (and 35 cu ft) of their potential turn pressure - twice as bad as when compared with 100's. Eventually you will run out of buddies willing to dive with you.
Now, doing it this way the guy with the highest SAC, not the smallest tanks, will still turn the dive as all the "thirds" are equal - and that ensures that anyones reserve third will be equal to what anyone used going in.
Still the thing is to be sure what fill you can get in the 104's. If all you can get is 2400 or 2640, you are hauling around a lot more weight (about 26 lbs) for no more gas than you'd have in HP 100's. In practice I get 3600 in my X7-100;s just about every where and that is 104 cu ft. I often have problems getting more than 2400 psi in LP tanks (outside of N FL) and 2400 psi in an LP 104 is only 96.5 cu ft. Not a great deal when you consider the HP 100 weighs 33 lbs empty to the LP 104's 46 lbs empty.
Plus, looking at the math above, assuming you can get 3500 psi fills, if even one of the buddies "only" has 130's, you are functionally limited to 1/3 rd of 130 cu ft, not 1/3rd of the 140 cu ft you really have in LP 104's pumped to 3500 psi so there is no real upside to carrying the slightly longer and heavier LP 104 if even one of your buddies has 130's.