Rank up gem for IMIW?
So here is my conundrum. I have a regular tech rank 4 gem and a 2015 tech gem. I plan on using the 2015 on duped SL or Ultron (like everyone else). I already have sparky at r5, and have Dock Oc and Yondu as 6*s. I have 7 other r4s. so this would jsut be filling out my roster with no intention of taking to r5. My question is should I use the regular gem on duped IMIW or hold it for Sentinel, Ghost, or a different tech champ. Thanks for any advice.