Hi Andy,
They won’t do any harm, but don’t run them too far back as the Sea Queen tapers in width to the transom, the chine spray rails are the most important to keep the boat dry. The Fairey’s are Deep Vee designs the sides of the hull are parallel so the spray rails can run further aft 🙂
I did retro fit spray rails to an old Sea Queen back in the 1970’s not sure it made much difference as it had a 35 cc two stroke engine fitted and was a guided missile, the SQ is not really designed as a planing boat but they will go but pretty well but unstable in the turns , the deep vee on the Fairey’s don’t have that problem.
Good Luck keep us posted, have done a build blog on here somewhere I have built 3 it’s a bit of an obsession of mine 🙂
Regards Ray