Some of what HS said is true. Your I28 and my Jeanneau Arcadia are probably real similar in specs. 30' LOA, 28 LOD, 24-25' WL, 5.5' draft for me, 2400 lbs of iron, 6500 lbs of disp. So to a degree, high tech sails help, but probably do not. The jib, more than the main. Altho if you can do as I can, my 195' main, 10' foot 32' luff, the tri- axil main is about the same cost as Ullmans dacron equal speced reefs etc.
i do find when it is wife and I, at 15-20 knots depending upon temps etc, a single reef and 110 is fine, good speed, level'ish boat etc. With a crew of 5-6 racing, I can get upwards of low 30's with a double and a 110 up. Altho a 70-80% luff and an LP around 100% would be a better sail IMHO for winds over 30 knots. Or the ability to reef the jib.
I feel the loose foot is easier to get the correct shape vs the non loose footed main. I can also get IMHO a better shaped main with 2 full vs all partial. I have not had a 4 full batten setup. The partials down below do make reefing pretty easy IMHO.
I would get a 155'ish sail with light cloth for those 0-10 knot days, Then over 10 or so knots, the 130-140 sail works fine. I came with a 135, had a 140 made for the lighter days.....should have actually gone with a 130, as I have a mini forestay to get the genoa around. A 130 would be easier from this standpoint. BUT, I like the performance of my 140 better all around frankly! That is a triaxle from Ullman. THe 155 is a string style. But that is used racing only. The others get used as needed.
Winter with colder temps, reefing, smaller head sails etc come upwards of 5 knots earlier than summer temps of say 60F and above. The colder air is denser, with more moisture, so one needs to reef/reduce SA sooner! Also depending upon how many people racing vs spouse and I will vary the reduce needs also. My main, I would probably do another 25-50% reduction when I get a new one on the first reef, and make the 2nd reef on par with a triple! This will not reduce my SA enough even racing to worry me, and give me a few more upper wind speed knots before having issues on those days. WInds above 20 or so are only sailed when racing generally speaking too! I have another 3-5 folks on board to help in these conditions. with spouse, we are motoring or down to a 110. Motoring is more the norm.
Hope some of this is helping, and the why I have the sails I do. Racing is a bit more use of my boat vs cruising. But I try to keep both uses, how many people on board, in given wind strengths as to how I will sail the boat etc.
Here is a pic doing around 8 knots with a 90% asym I have, at times I wish I had the full rated spin.....some day. I have a wider post fastnet half ton rear end, vs your rear that is narrower pre fastnet rule changes. If BP gets into this, well, it is what it is! You still have a nice boat for what it is etc.......