When I first started foiling (4 years ago on slingshot and 121L Starboard slalom board) I tried a few things to keep the nose down...

I built some extensions for my footstraps to get them more forward. Totally unnecessary.

I rode with the sail right at the front of the mast track (caused odd twist in my body). Totally unnecessary.

I had heaps of rear shims (especially Starboard race setup). Totally NECESSARY especially when learning to control a new foil!
Over the 4 years I've learned a lot!

I've had sessions with the mast at the back of the box (and wanted it further back!)

I've moved my footstraps to the middle position at the front (and fully extended front hole to rear hole for the back strap)

I can ride with/without shims depending on the swell (smoother is easier), gustiness, and target speed.
The 3 biggest tips:

1. The harness is your friend! You get much better down force via the mast than your front foot!
Use long lines so you can still sheet out while staying hooked in, because even when you sheet out, you MUST keep downforce on the mast. If you are flying high in a gust and need to sheet out... only do so a little bit, but keep your weight in the harness (for heavens sake you'll end up aiming for heaven if you don't!). The back hand controls the nose, more sail-power for down!

2. Control foil power by angling the board to windward. The more you lean the board (and foil) over, the less lift you get upwards, but arguably more lift to windward. So how do you pivot downwind... move your hands back along the boom, push the mast forward over the nose and sheet in, the forces will push the nose downwind... and you WILL accelerate! Be ready to flatten the board to gain lift when you need it!

3. Each foil has a preferred mast base position AT DIFFERENT SPEEDS! At 20kt top speed I'd have a rearward position to help get the board flying in lighter winds. As I hit 30 knots VMAX, I need the mast much further forward, as much as + 5cm, since my small speed wing is making as much power as my largest course racing wing at half the speed. If you are hooked in, sheet in on a gust and the nose goes down, move your mast back, but if you go skywards or get scared, move it forward.

4. Shims definately help, they do add drag, but if your not in control your not going to be fast either. Fast is relative too.

5. Move your hips! Long lines help shift the balance point fore-aft as you slide your hips fore-aft, but also lean into the harness.

6. Foiling involves a delicate balance of so many different forces (4 winged surfaces, 4 weight points) so when you make an adjustment, make a much smaller adjustment than you would on a sailboard. ESPECIALLY with downforce on the mast. E.G. if you unhook, you need to use arm pressure to maintain downforce on the mast base.
OK so a few bonus points.
Happy foiling!