i tend to move my larger sails up/forward and back for smaller sails
in the mast track that is
then i read about a formula sailor stating:
"The general rule of thumb is that the bigger the sail, the further back it is positioned on the board. Bigger sails weigh more and tend to settle the nose of the board and are often sailed with larger fins which have the same effect. Smaller sails weigh less and especially when combined with smaller fins tend to unsettle the nose of the board so moving the mast forward will counteract that trend."

is it different for formula or ???

and yes i am aware that some people just keep it @ 135 cm

kato:
i am NOT questioning the idea of moving the mast foot
just the WHEN
do larger sails typically go forward or back on the track for you ??

thank you for the "useless" information - no info is useless !!
generally my large sails are further up than back
THIS contradicts what the formula sailor was suggesting

that's all

just more useless info - i guess {sorry }

Chris & Brett +1

I think it's a balance between board, fin and sail size, when that's right I think the mast base position will stay the same for each sail. That's what works for me any way, right or wrong. I use two sails with my favourite slalom board and have the base in the same position for both, back a little from centre of track.

Try this ....the center of effort on a 7.5 will be different to a 5.0 so would you have the same position on the mast track. For me no,the large sail is further forward than the small sail. The C of E difference between 2 sail sizes is very small so you may not notice any board trim changes.If i ran the 7.5 at the 5.0 mast setting the fin would keep spinning out from too much back foot preasure.
A formula board behaves and drives differently to a short board so it makes sense to use the weight to control the nose.
Please note that i use a "Barn Door" very rarely and am much happier on a short board in 12kt or surfing