Don,
Give the gang some more info to help you.... ? What length are the 50-55's ? What tip weight are you shooting ? The only way for sure to know if you are spined correctly is to bareshaft. I know it is painful to cut the feathers off perfectly fletched arrows, but ya got to do it. Cut the feathers off three and shoot them with 3 fletched shafts and see how they fly and impact with the fletched shafts. I would just about bet you are too stiff right now and need more point weight, or more length on your arrows. I realize you cannot add to length of these 50-55's, they are what they are, but if you wanted to try more you could start with a given point weight and full length shafts and start cutting them 1" at a time until they were spined correctly. Just remember heavier tip weakens the spine as well as longer length. Lighter tips stiffens the spine as well as shortening the shaft. You will also need to set your brace height to what the bowyer recommends and keep it there for tuning your spine. If it changes by 1/4 -1/2" it will affect your spine. Also make sure your nock fit is perfect, a light bump on the string should make the arrow fall off. Do not forget to hold the bow as close to vertical while bareshafting for spine as well. A cant will give you a false reading sometimes. As you cant the bow you are also involving the nock point setting and can cause a false reading of spine. Nock point setting is what controls the up and down flight of the arrow. Most bows shoot well at 1/2 to 3/4" above square. If it is too low then the arrow will bounce off the shelf and cause porpoising and noise. If you shoot 3 under you will need 3/4" above square most likely. I am no expert , but just my humble opinion and what the gang has taught me. Hope this helps.
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