I don't have the room to build huge armor columns but I do have a few multiples.

Cobra
2 25th HISS (black)
1 25th HISS (blue)
1 25th HISS (red)
1 DTC HISS (modified)
4 25th CLAWs
4 25th FANGs
4 25th Flight Pods (white)
1 25th Flight Pod (blue)
3 25th Firebats
1 25th Rattler
1 25th Water Mocassin

Joes
1 25th VAMP
1 25th VAMP (customized)
4 25th RAM Cycles
1 25th Armadillo
1 25th AWE Striker (green)
1 25th AWE Striker (tan)
1 25th MOBAT
1 25th Night Spectre
2 25th SHARCs
1 25th Conquest
3 25th Sky Hawks

And I have some custom vehicles as well but these are my G.I. Joe vehicles I've "armor" built.

Imagine having a dozen Hiss tanks as a kid... The battles would have been awesome, no doubt, but storing away your toys afterwards, that would have been quite a chore... :(

Anyway, i don't have dozens of any vehicle. Not even quintets. Three of a kind, that's the maximum: three RPV's, three Stingers, three Adders. I have this thing with missile artillery, see. Then some twosomes: two Fang II's, two Ferrets, two Desert Foxes, two Demons. Other than that, only singles.

My armor collection is limited, but only due to pickiness...

3 HISS tanks (version that Fireflyed uses in pic)
2 Night Humvees (customed)
1 HULK Buster Humvee (customed)
8 X-30 Conquests (4 custom, 1 "melted", 3 incomplete)
2 25th VAMPs
1 Hurricane (customed)
4 HAVOCs (2 customed, 2 incomplete)
1 Rolling Thunder
1 Avalanche
1 RHINO
1 semi-truck base thingy whom I can't remember its name, but its newer.
many misc non GI Joe vehicles

I uploaded 2 old photos of my HISS collection in the Collections area.

12 vintage (one is gunless)
2 (plus one mint) HISS 3
3 Septic Tanks

Plus recent (not shown)
3 Crimson Sabotage Hisses
1 Target Hiss
1 25th black Hiss

And 2 complete HISS 2's, 1 incomplete, 2 HISS IV's, and 5 or so DTC HISS's.