Best online resource I know of is sailwarehouse.com - they list your boat (and mine!) with all sail dimensions. They also provide a ‘how-to’ measuring chart and explain what the I, P, E and J all mean.
They carry sails by Rolly Tasker who is well known in Australia and about the Southern Ocean. I ordered a 135 from them last August. They did NOT have it listed for the H25; what they suggested is for me, once I could cite the correct sail dimensions, to just search for any other boat’s sail that fit my luff. What I got was a Cape Dory 25 headsail.
The 1st-gen Hunter 25 as designed by my dad is notably tall in the rig. He was a B24 pilot who knew the worth of high-aspect aerofoils. So looking at any other boat’s headsails is likely to mean you’ll end up with more foot that you’d expect. The Cape Dory 25’s 115 is a perfect 135 for the H25 (13.5-ft foot).
Just be careful ordering mainsails. There is almost no other boat for which a ‘stock’ 6-oz mainsail will be 24.5’ on the luff and only 8.0’ on the foot - a CD25 for example will be like 10-11 ft. My boat came with one at the right luff but only 7.75’ on the foot which I believe had to have been the mizzen for some ketch of about 35 ft.
Read the sailwarehouse.com site carefully. You’ll be grateful for the education.
