A 6' x 4' fan is a small one!
Get yourself an old roller blind and replace the cotton blind with a polythene one - no storage problems! But make sure you keep summer sun off the roll or it will shred.
Cover doesn't have to be 100% to work because covers are 100% efficient.
A cover that is 3' 6" wide will give 100% protection to at least the central 3' where all the peaches are, and may protect the full 4 foot width...
You can start the cover 2 or 3' above the ground and it will still protect everything more than a foot off the ground (unless you live on open moorland and have horizontal drizzle as a norm).
Using chemicals against leafcurl is a mug's game.
You can even use opaque covers because 80% of the damage happens while the leaves are bursting, before they are really helping the crop. You can use anything - corrugated iron, old garage doors etc.
If you take an opaque cover off and expose the whole tree as soon as the first full-size leaves develop you will probably find you still get an 80% reduction in leafcurl.
Cheers.