Need to measure yourself
That won't help you. You need to make the measurements yourself, especially if you have roller furling, as furlers are often owner installed, leading to different sail luff lengths due to variance in foil length. See attached link.A big difference for the L28, is probably the same as observed for the L25. The older boats have the mast further back with a compression post in the cabin. The Mark V L25's have the mast further forward (J=8 feet vs. ~10)with no compression post. It is not required as the mast step is closer or over the bulkhead.I had a jib damaged in a storm and spent a lot of time looking for used. Just a thought...I am reasonably sure the rig for the L28 is identical the the L25...I really miss all the info on the original lancerowners site. If so, the dimensions of a Catalina 25 sail are similar from a height perspective, only due to my much smaller J, a 100% jib for a Catalina 25 would be a 145% genoa on my boat! The cloth would be too heavy though...but if I was desperate...Bob