HI Mandy
Its Rob Kemp from Kemp sails,i have a Dufour 34E hence being on this forum. We have built many sails for the 365 and its quite common to reduce the head sail size, the smallest we have ever done was 118% but this sheets right at the front of the Genoa track, lifting the clew would help move the car point aft but this tends to be a bit of a compromise as the clew would look a bit high. I would suggest an over lap of 125% would be the best compromise if you are looking to reduce the area as this would allow the sail to be working at its most efficient is the sweat spot of wind range for the boat.
On the main assuming you have the continuous line reefing common on the spar craft and z spar masts lifting the reefs is not an issue. If you have for some reason a Selden single line boom ( some boats have swapped to these) then the reef heights are defined by this system so cannot be changed significantly.On MY 34 i have a Spar craft set up so i have fitted two deep reefs with no third. Also i used Loop low friction rings on the luff and leach of each reef to help with the friction in the system. Tapered reef lines are on my to do list which also help but have not had time to do this yet!!
Sailcloth is big subject so probably worth a telephone conversation. Personally i am a big fan of Vectron which is a hybrid woven, i have this on my boat. Its a fair bit more expensive that normal premium end polyesters but will last significantly longer in terms of shape stability so if you plan on keeping the boat for several years its worth consideration.
Hapy to have a chat if you wish regarding any of these points.