Everything about a large blimp is the same as a small one, only slower and with more people.
Inflation takes longer than you think
Filling 1,510 cubic feet is not a ten minute job. Allow real time for the first inflation of a 25 or 30 foot blimp, and plan the cylinder handling before the day.
The smaller sizes genuinely are a ten minute one-person job once you have done it. The large ones are not, and anyone who tells you otherwise has not filled one.
Anchoring
Lift scales with volume, so a large blimp pulls considerably harder than the three pounds a 13-footer manages.
Plan a proper anchor point rather than a sandbag. This is the one place where the larger sizes need engineering thought rather than common sense.
Storage and folding
It still folds flat, and polyurethane still tolerates the cycle. It is simply a larger, heavier package and usually a two-person fold.
Do not fold it frozen, and give it somewhere dry. A large balloon left damp and folded is the one storage mistake that actually costs you something.
Print area at size
18 ft: 52 by 108 inches. 21 ft: 52 by 144. 25 ft: 56 by 168. 30 ft: 60 by 192.
Enormous, and still keep the message to three or four bold words. More room does not change how long a driver looks.
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