we stay at Le La Bleu camp site in Doussard and you can launch off of their 'beach' FOC if you are staying there.
Bienvenue au Camping International du Lac bleu
There is a public slipway next door at the marina too.
Deffo need PB2, ICC, CEVI, Insurance, SSR, you must carry a copy of the lake regulations with you at all times, must fly a lake specific blue water ski flag if towing and last year the lake police started to impose the need for flares to some of the larger boats but i'm not sure if they be imposing that on sibs.
fantastic place to stay/ski/boat - couldnt recommend it highly enough