JJD, as I recall:

Silkair:
A bit more old-school airline style – you get 20 kilos of baggage allowance and you have to pay for every kilo over that. I've never carried a surfboard on Silkair, only a twin tip and had no problems.

Tiger:
I didn't have any trouble with my kite gear including a smaller surfboard, but make sure you go online a few days before to pre-pay your baggage, and be sure to select the 'sports equipment' option. I had about 23 kilos of kite gear and it was about an extra $35 each way, which IMO aint bad.

Burls