There are two types of Cabomba normally available - Cabomba caroliniana and Cabomba furcáta. It sounds like you have the carolininana variety as you are doing well. If it is growing upwards very quickly but spreading out this could be an indication of too little light. I have put the tropica info for each species below, and also included the alternative suggested for lower light levels.
From www.tropica.com
Cabomba caroliniana
Family: Cabombaceae
Continent: South America
Height: 30-80+ cm
Width: 5-8+ cm
Light requirements: medium-very high
Temperature: 18-26 °C
Hardness tolerance: soft-hard
pH tolerance: 4-7
Growth: fast
Demands: medium
A very popular aquarium plant owing to its beautiful foliage. The least demanding of the Cabomba species, but still causes problems in poorly lit aquariums. If there is not sufficient light, try Limnophila sessiliflora, which requires less light. Most decorative when planted in groups. Eaten locally as a vegetable.
Cabomba furcáta
Family: Cabombaceae
Continent: South America
Height: 30-80+ cm
Width: 5-8+ cm
Light requirements: high-very high
Temperature: 22-33 °C
Hardness tolerance: very soft-medium
pH tolerance: 3-7
Growth: fast
Demands: very difficult
A very beautiful but also difficult plant because it requires more light than most aquariums can provide. Soft water and CO2 addition are also necessary for optimum growth. Death of lower leaves indicates insufficient light. In good conditions Cabomba furcáta develops small, long floating leaves and often forms beautiful purple flowers. Should be planted in groups, but not too close because the light has to reach the lower leaves. Used to be called Cabomba piauhyensis.
Limnophila sessiliflora
Family: Scrophulariaceae
Continent: Asia
Height: 15-40 cm
Width: 4-7 cm
Light requirements: medium-very high
Temperature: 22-28 °C
Hardness tolerance: soft-hard
pH tolerance: 5.5-8
Growth: fast
Demands: medium
Limnophila sessiliflora is a good and undemanding plant which is a good alternative to Cabomba, which demands a lot of light. The plant often grows leggy in poor light, but this can be counteracted to some extent by stimulating growth by CO2 addition. Most beautiful when planted in groups. In good growing conditions it sends out runners and spreads across the bottom. L. sessiliflora used to be called ''Ambulia''.
HTH, Eddie