Here's my summary:
DOUBLE - or Mahoi. This beautiful Cavendish type has very wide, dark green leaves and produces a full sized fruit. Also called the Mahoi, the second generation produces multiple bunches of fruit, usually 2 but sometimes more. Height 5-7 ft. Mahoi, Mai'a mahoe (Twin banana). Type AAA. Same as the common dessert bananas in groceries. You care for it like a cavendish, same requirements, and same susceptibility to cold. Good for outdoors in zone 10 and above. Not recommended for backyard planting in zone 9 and below if you want fruits. Can be good container specimen but rarely bear double bunches of fruits in containers. Needs its corm and mat to be well developed before spitting out double or triple bunches of fruits.
Here's from pitangadiego's site:
DESCRIPTION: DOUBLE
This beautiful Cavendish type has very wide, dark green leaves and produces a full sized fruit. [T]he second generation produces multiple bunches of fruit, usually 2 but sometimes more. (001) (010) Rare and hard to find, [it] has the ability to produce 2 or more bunches of sweet bananas at the same time. Mahoi means twin in Hawaiian. (052) Dichotomous fruiting head. From a single trunk this mutation of a triploid Acuminata produces two flower buds. The plant resembles a dwarf Cavendish, growing a single bud for the first generation, then doubling as it reaches its' full size. Tender. (009) This is a somewhat imprecise name referring to a mutant that produces a fruit bunch that divides into two as it grows, i.e. it is dichotomous. {NOTE} This mutation has occurred in three different banana types in 'Dwarf Cavendish and 'Gross Michel' in the AAA group and in 'Maia Maiole' in the AAB group. At the time of writing I am not sure to which of the above this plant belongs. (011) Two to four heads of sweet fruit resembling the cavendish in taste and size. First generation may only send out one head (063) Stout trunk. Sweet tasting, similar to Cavendish. Called Double because its' second generation can produce two (or more ) large heads of fruit simultaneously and may weigh over 100 lb. (105) [Fruit is perpendicular to the stalk. (038) Mahoi is a mutation of the common dwarf 'Cavendish', and grows similarly. This cultivar almost always produces two large heads of fruit and can occassionally produce a third. This sweet fruit is highly rated and it can ve very productive. This is a rare and unusual Musa. (031) (032) (040) All the varieties [of banana] were kapu (forbidden) to woman except for three types. These types were mai'a hapai (pregnant banana), mai'a popo ulu (breadfruit-like ball shaped banana) and mai'a mahoe (twin banana). (107) Mai'a = banana.
TYPE: DESSERT
GENETICS: AAB (Maoli group) (006), AAA (009)
HEIGHT: 5-6' (001), 5-7' (052), 4-8' (009), 7' (038)
HIGHLIGHTS: Multiple Fruit Heads