I did some test builds last night with my TE, build weap 6/7, negotiate 5, station faction +14k. As I went through my weapons, I noticed lvl 5 were around 175%, so I figured I would see how many lvl 5 weapons I would have to build to get up to 200% (above 195% average). I used the custom buckshot gun as my test weapon - all vendor parts (to eliminate upgrade % increase). Results: Per every 25 built, I noticed a slight % increase (approx 3 - 5 %). After I built 100, I was able to achieve a steady output of 195% - 199%. I was unable to achieve 200% without the use of a terminal controller. After completing this, there was no effect on higher lvl build % ; meaning that building lower level items will not boost % for higher level items.
If anyone else has input, or data to help upcoming builders, please feel free to add on your results/suggestions!
~Beast