Re: TAC 15i.......Unbelievable!!!!
I hope all is going well with you, since we last spoke.
In relation to your question about "Spine Testers" the one I and most people who are serious about building precision arrows is made by RAM Products and it's called the RAM QC Arrow Carbon Spine Tester.
RAM Products can be reached at: (208)-882-1396 or online at their website.
You can also purchase one frmajor archery distributors like Lancaster Archery. The price is usually around $299. I've had mine for years, but it paid for itself with the first couple dozen arrows I did and I couldn't live without one, since I will only buy raw shafts, then sort, match and build them out myself. You might say I'm a bit picky with my equipment, but then in competition shooting it's the norm.