Chinaman.

Before you even thinking of going to tribunal, please check and make sure the project is under Schedule H. From your LAD 8% i am quite certain this is another version of SOFO/SOVO that u bought. MCT sold a lot of such projects. Schedule H the LAD is 10% for parcel + another 10% of balance 20% purchase price for the common area deliveries. 

Otherwise you might just waste gas.

If that is the case, you can't go to tribunal. It is either you group together with all buyers and bring them to court (after the risk vs reward analysis) or just accept the payment and move on with your life.

Bro, is the dev willing to pay full 5 mths late charges based on discount price ?

If it is, then I advise u to take it. Else, legal process delay longer and u have to pay legal charges and the processing period also unable to get the key while paying the full bank installments. Not advantage as a buyer.

Btw, I feel its fair if they give LPI based on discounted price since that was the actual purchase price. If it reflected into the S&P, then all purchasers kenot pay 2% and enjoy 8% disc while obtained 90% loan dy.