to install an old orthography Malayalam Unicode font which is required to read the posts below]
At least, 3 of the chillu forming consonants have half-forms different from chillus. As the first example, half-na is highlighted in this image:
Notice that half-na is not chillu-na. Below, we can see the half-consonant in action forming conjuncts with various characters:
Simillar to ന(NA), ക (KA) and ണ (NNA) also have following half-forms:
Their conjunct formation examples are: