Herbert;
Welcome to the forum. Now, I do not claim to know a whole lot about arrows... Generally, for every inch under/over 28 inches of draw length (for most bows - some are measured differently, such as XX#@26") you need to subtract/add 2.5 or even 3 lbs of draw weight to find the correct spine for your arrows. Since your bow is rated 55 lbs at 28 inches and your draw length is (according to what you report) about 26 inches, you should *start* with shafts spined 45-55 lbs; the closer to 50 lbs you can get them, though, the better (if the actual weight is what it has been rated at) -- especially if the bow you have has little or no arrow shelf (it's ok to use stiffer shafts, but they might not be optimized for your bow/draw length). I use a Martin longbow rated 50#@28" with minimal shelf, draw to 29.5 (approx.), and use 125g. tips on Cedar shafts spined to 50-55 lbs. There are others here who know a lot more about the subject than I do, and I hope they will chime in...
By the way, I have read that some newer bows are measured from the string to the arrow plate (or equivalent) at full draw, instead of from the string to the back of the bow at full draw. If in doubt, ask the manufacturer of the bow.
As I said, I am not an expert on the subject, even though I have been making my own arrows for the past nine years.