15 kg in 3 months is definitely doable in my time during the mid
'80s, also at Delta Company in the old Tekong ITD BTW. Didn't have
PTP then, some more.
Basically, it involved jogging in vest-&-sacks every morning
(while the rest of were doing area-cleaning), followed by tekan
sessions before every meal-time (leaving recruits too worked-up to
eat properly). Survived mostly on night snack, as I recall.
Luckily, it was chilli or vege bee hoon most of the time, &
recruits were allowed to consume as many plastic-mug-fulls as they
want.