The Naish 125l was the board i started on (95kg). Once i got gybes and touchdown foot-switches I moved to a 99l Armstrong board (took a couple of sessions to get used to it). The even bigger 135l Armstrong board should be a tank and very stable. Is there any reason you didn't get a smaller volume board (maybe around 100-110l)? That's normally what folks thinks makes it more fun once you get the basics - an even bigger board will feel more sluggish etc.. See if you can get one of the more experienced riders to try your board.

Your front foot generally should line up with the front foot strap inserts. If you're falling off the back, probably means you either (i) need to stand forward, and/or (ii) move the foil back a bit (assumes the foil is too far forward and you can't get weight forward enough to keep the foil down).

Try the old balance trick to see if your board is roughly balanced. Hang your board upside down from your fingers placed a third of the way back from the front of the foil & see if it lies parallel to the ground. This will give you a rough indication of if the foil is in the correct place.

Ron54 said..
Naish hover boards are a very stable,forgiving unit,feet position not an issue

Ive always run the foil at the front of the box to trade speed for lift,trying to keep up with faster boards.

Feet position can always be an issue on any board and foil. Remember when on foil you're not riding the board you're just riding the foil.

Running the foil mast at the front of the box only 'increases lift' if you keep your feet in the same position - foil position is 100% relative to feet position.

I think you've identified the issue there and you can solve it by standing further forward (as you say) or moving the mast back and keeping your foot position the same.

No need to slam the mast all the way to the back of the box, you might be surprised and find that movement of one or a few centimetres is enough to solve your issue.

I think you hit nail on the head with the "old and useless" in terms of your mindset. I watched a friend who's near 70 and an ace kiteboarder, and before that, windsurfer try and try, and always get on foil then fall off the back. Finally quit and just does what he knows. You need to approach foiling like a balance board on a roller. If you are timid in anyway to get the balance board level, you're going to go up, then fall back. You just have to learn to unweight and then use your weight on return to level out. Foil lift point as above post (the Kane Method) is a must, otherwise with foil lift not balanced with board, you will have to compensate with awkward pressure on front or back foot. The sail is there to provide momentum, but you need to use your weight off and on to pump the foil and be balanced over it. In general terms, falling off the back means you are waiting for the sail to pull you, and to keep your balance when it does, you are shifting your weight back to resist the pull. Instead, start making a more up and down rhythm pulling the sail/wing from up to down while lifting your body to unweight the board and foil. Lots of helpul videos with a bit of google search, but I've always liked Alex's: