**UPDATE**
Alright, well after thinking I had things dialed in, there were still some inconsistencies. I felt that unless my form was absolutely 100% perfect, I was still getting some erratic arrow flight and perhaps some false spine readings like some of you had mentioned.
I went back and wrote down everyone's advice and decided to start from square one.
1) remeasured brace height and it was still in spec. Check
1.5) (too lazy to change all of the numbers from here down as this was an afterthought worth mentioning.)
Double check draw length 27.5" on the nuts and clicker directly attached to string with with timing cord. Check
2) marked my "new" nock point and my old nock point to use as reference. (There was almost 5/8" in discrepancy here) Check
3) re-tied my lower nock point and left it just loose enough to move around. Check
4) double checked my draw length and weight (58# @28" widow, I'm drawing 27.5" at about 54/55lbs) Check
5) check center shot....hmmmm. Well, I went ahead to double check that and something seemed off. I know I had checked it before but I figured my dad had shot it like that just fine. (perhaps he did but it "worked" for his shooting style?
At some point after he bought the bow, my dad put a almost "velcro" looking shelf/riser pad on this bow. I think it originally came with a much thinner calf-hair setup. So I took a closer look and decided that it needed to go. I ordered up a small one-piece calf hair pad from BW and got it slapped on a few days later.
New, thinner strike pad installed. Check
EDIT: For clarity, this is when I realized that my center shot was off and the thicker riser pad had been giving me false weak spine readings.
6) At this point, I have my bareshaft cut down as far as I want to go and have a similar length fletched shaft and I give it a go.
(Perhaps I should start over again with a full shaft and cut down but I think I can get to where I need with what I've got but I may end up a bit heavy with my arrow weight.)
My finding at this point: my previously perceived weak-spined arrows are now consistently showing stiff (like many of you mentioned but my previous setup was giving false weak-spine readings).
My form may not be stellar, but when I'm not fatigued, I can stack them in there, and realize when I've made my own f-ups. I'm now seeing consistency but also that I do in fact, have a stiff arrow (like many of you previously questioned).
I decided to take out the aluminum insert and add a 50gr brass insert.
BS and fletched are getting closer with the 150s but still not quite there. I try some heavier FPs (175 and 200) and boom, we're there but still getting some slight porpoising.
7) Glued in the heavier inserts and FP combo to correct the spine issue Check
8) I'm getting close and just want this figured out but I decide to take a break for a few hours so I can come back fresh for wrapping this up.
9) This was my favorite point of this whole ordeal as everything was finally coming together. I simply had to do some minor tweaking of my nock point and soon I was slinging 620 gr darts down range with perfect flight when I did my part! All of a sudden this bow/arrow combo has a degree of forgiveness which it never had before and does so with a level of stealth worthy of being taken to the whitetail woods.
When my form/release goes to hell, my points still group but only then do I notice some erratic nock travel with a foam block target.
This is in stark contrast to my constant chasing of nock left and slight nock right.
10) Lastly, I wanted to move to a tab, but old habits die hard. I went ahead and tried a new glove while I was at it. I can't say this helped a ton but my old glove was worn out and about 20+ yrs old. This stick-tite glove is the cat's pajamas and was exactly what I was looking for. YMMV.
While I ended up with a slightly heavier setup than I was anticipating, I'm going to give it a shot and see how it performs at the 3D range. I'm hoping to see what it chronos at this weekend. It appears to shoot anywhere from 150-200 grain field points well with the sweet spot being 175-200s. I still have the 400 spines to try out and I may tackle that as it starts to warm up.
Is it common to have some degree of wiggle room when it comes to broadhead weight? If I stretch past 20 yards, will I start to see some variance and need to settle on a specific weight?
I hope this provides some degree of useful information as a lot of great info/advice was shared by others offering their insight to help out.
Thanks again!