Hi

I would certainly recommend cutting sections of fabric to cover the sides of your mould with, separate from the main horizontal piece. Give the fabric a mist of spray tack before cutting to give you nice sharp cuts. A roller cutter works well for this (Olfa)

Give the surface side of the fabric another mist of spray tack before carefully placing onto your mould sides. For ease of lay-up, it might be a good idea to lay-in separate pieces for each side of the mould, unless you're confident with being able to cut each section to the right size. Once you've got one or two pieces in, you can likely overlap the remaining pieces

The main horizontal piece of fabric can then be cut slightly oversize and allowed to overlap the vertical sections a little. Again, a mist of spray tack will help it stay in position well. Carefully smooth it into the mould from the centre and then into the corners.

It is possible that you're mould might have become porous, if you've lost a little of the surface gelcoat, but it's more likely that you've just got a leak in the bag somewhere. It's sometimes good to try and rely on less pleats that are of a bigger size, which might reduce the possible sources of leaks in your bag.

If you've gone around your bag pressing all of the tape against the mould and still find that you're getting a leak, though, (including around your entry/exit lines) you might want to consider envelope bagging it instead

This might be preferable if you're only looking for a one-off part and don't intend making loads of part from the mould

Be prepared for a tough job getting the final part out of your mould also, as it looks like you've dealing with some quite steep parallel sides there