IMO the gap @ the bottom of the taper comes from bridging, although 2 piece (moving core) can also add a bit. So, solid, one piece core is the base.
Taper shape consistency/quality is very important. The surface of the taper has to be flat!!! You can get best results by pulling the top core part along a fixed sanding belt at desired angle.
What worked best for me (when vacuum pressing) was steeper taper angle (60-70° od oka), no round @ the top (just remove the sharp edge). A consistent round-out at the bottom of the taper is very hard to do even with a filler, so it might just f*** you later and you have 2 steps more (also sanding). Most important here is how you do the layup!
Cambered edge is much harder to do without having air gaps, so I avoid it.
First part is not so relevant as the second, but it might help.
I lay down a clean plastic film (PVC) on a flat, clean (no dust, shawings,...) surface. Than I started with peel-ply and FG sheets on top, align them, smoth them out, than soak with resin, and smoth it down a bit more, to get a compact sheet.
Than I soak up the core (since it has a bit of rocker already I put wooden blocks under the tips to prevent it to flex later, so the FG stays in place during layup).
I get help (far less air pockets). We grab the plastic film and invert it on the core, starting from the centre. A third person to gently apply presure (smoth out) while you are slowly lowering the film is a great +. The tricky part is to remove plastic film since resin creates a bit of vacuum. You have to be very slow. Use help to pull the film and you hold down the fibres, so you don't pull them from the core or ''delaminate'' the FG and Pealply sheets, because you would get airpockets to deal with along the way.
I use my bare hands (with gloves) and a credit card. You have to do this as perfect, as you were doing a hand layup, and you will get great results. First smoth out the fibres on the top surface with your bare hands, starting from the centre out also forcing excess out.
Than lift the laminate off from the lower core surface and wiht your other hand tapp with your fingers on the taper surface starting from the top edge down and do this along the taper. Than do this again with a card, but not with tapping. Just slowly and gently smoth down the sheets.
Than push the card in the corner (where you got air pocket) and tapp with your fingers and smoth out the sheets from the card (which you are holding) out, and work it along the taper. Repeat the smothing out with card (2nd one, or just push down with your fingers @ taper). Be carefull how you are removing the card. If you pull it directly off and far worse, if you tuch sheets with the card's surface, you might pull it off and create pockets. Slide it along the taper while lifting.
At this stage you should have a perfectly hand layedup board. Check for any potential dry spots and apply some resin if needed, otherwise (gently
) throw your board on rocker taple, breather or watever on top (same procedure along the taper (lifting breather from bottom surface))..... and do your vacuum set up. Usually no additional smothing out is needed after applying pressure, but if not, use a card, not to create bridging with pulling cloth out.
At this stage I asked myself WhyTF do I even need to vacuum? Just to f*** with vacuum setup and leaks and stil not sure what's the result beneth the breather? Yp, I started pressing and also got rid of breather and peel ply and introduced plastic top sheet, which adds to durability, however turns on the head the complete above mentioned process.