I have been using my Sabfoil/Moses 790 (85 mast, 90 fuse) on a fin slalom board (iSonic 80 cm wide). I am now looking for a windfoil board to achieve better balance (front/back, with shorter distance foilbox-mast track; and sideways, with "flatter deck & wider tail"). Any suggestions or experiences with this foil on a foil board (foil/tuttle fin box)?

I have first foiled the 790 with my iSonic 80 too. But indeed it was not well balanced. Then i got the Alien 125 and it was great. If you are looking for a new board i would suggest to get one with both systems dt and rails like the Stingray or JP FreeFoil. With a plate adapter for your mast you have a great option to tune your stuff.
www.groovekiteboards.it/deep-tuttle-adapter/

PatK, thanks for relevant experience and board suggestion. And the adapter (dt foil on rails board) that you linked to, is something that I have been looking for. Looks really solid. As you mention, a combo dt/rails board would be great.

This one would be good

www.kingofwatersports.com/product/jp-hydro-foil-pro-135-windsurf-board-2017/jp-hydro-foil-pro-133-windsurf-board-2017

But any freeride windfoil board with a deep tuttle should be fine

Thanks! I found the JP 135 (can be combined with race foils from same seller) and JP 130 (freefoil) used nearby. Ideally it would be able to handle foils like a SB Freeride, in addition to my 790. I am a little skeptical to both: Freefoil rear straps significantly more inboard than full width. 135 too wide for the 790 mid/low aspect, while jumping on the race foil will reduce my low-end (and reason for foiling)? Available new (more expensive) in shops nearby: Alien 125 sounds maybe more middle ground, so does the SB Freeride 125. Stingray 125 HRS on sale, but wrong "shape/setup", and LTD full price. . these choices...

A friend told me today he ordered an Indiana 122L for his SAB foil 950/999. Looks nice.
shop.indiana-paddlesurf.com/foil-boards/wind-foil-boards/indiana-wind-foil-122l-carbon-with-bag.html
You won't need the back strap often. I only use it for going upwind. The 790 likes inboard strap positions. The race stuff outboard pos.
Just look Balz on the 790 (video). His board is so narrow. You don't need a board 80 or 85cm wide
www.severnesails.de/moses-twist-balz-mueller/

adventuresportsusa.com/products/22-free-foil?variant=42763686117596&gclid=Cj0KCQjwu-KiBhCsARIsAPztUF0F8k6JxerxC8uw6lHTjSWtAXPHzfCspeoiG8xJRPS0RQ2UOCArrQoaAmbeEALw_wcB

If thats the JP 130 there are some real advantages to tracks although it does look like there mast track is further back on the 130 which is good for maneuverability but not ideal for learning to gybe.

If JP 135 cheaper I would go with that for sure. The 130 is a bit large for an carving board so unless you are 100kg I don't think it would be come your advanced board, the 130 will do way better if you want to use bigger sails and focus on speed.

Of course, most windfoilers succumb to winging peer pressure eventually so maybe that 130 makes sense

Thanks for all the Ideas. Not heard of Indiana before. Looked like a good size. I have been thinking.

What I like with the Freefoil 130 is having both a DT box and US track. My 790 needs DT, but I like the possibility to utilize the track to tune the balance of the setup (although with a different mast or adapter). And I expect that this and similar boards can handle a bit faster foils if I want to explore that direction a little bit (Freeride, not race). And if I would get more interested in exploring Wingfoiling, it works well enough to get a taste of that as well. Even though the width is 77 cm, the tail is narrower - 60cm ofo - and I am uncertain wether this would be a significant disadvantage, but watching multiple videos with Slingfoil wide tails, it does not look like people use the full width on those kind of boards. Even though the length is 207, the mast track is fairly close to foot straps, thereby being more maneuverable than SB Freeride of same length, but not quite the Slingshot class.

Even though newer boards, like last years SB Freeride and 2020 FoilX looks like interesting design ideas - faster & easier takeoff (?), and a bit wider tail - I wonder if the difference from the 130 will be significant (FoilX probably most similar, Freeride distance to mast track a bit longer).

I think that the 135 asks to be driven with more racy foil, and I am not sure whether I want to go in that direction. The current owner has tested it with a lower aspect foil, and struggled with the balance. He can include two older F4 race foils with 105 mast into the package. I am a little tempted, but believe that I might prefer a somewhat slower foil.

Shoot - where is my reasoning failing..? Probably in several places.

Goya Airbolt 122 fits perfect

About the right size, but pretty narrow in the tail. Pretty fancy bottom.

You want tail width if using larger sails is a priority.

Thanks for all the great advice! I got the JP Hydrofoil 135.