I think that’s in your head, yes you can go to heavy but most of the time I use 200 gr/m or 450 gr/m as a first layer.
Most of the time a very thin fabric is harder to infuse.
My moulds are typically tooling gelcoat and then 1 x 225g CSM hand laid.
Once cured carry on with mould layup whether that is infused or hand laid.
Thanks everyone for the answers. Fasta, I was thinking to your solution, but I was scared about mould delamination. Do you ever faced it? I don’t need my mould to be very productive: 20-50 pieces are enough.
Mould delamination or Pre-release usually happens due to resin shrinkage and then especially near corners. Whether or not this happens depends on a few things like how much does your resin shrink, the mould/product design and shape, weather/temperature stability day and night with plug expansion and contraction, and then also your release system.
I use specific mould tooling resins that are very low shrink or no shrinkage so this is the main thing to help avoid any pre-release.