We sort of covered this above, but here's a little more perspective. I'm sure
@MT406 will be able to give some great input after a couple trips.
Looks like the Slipstream 96 is 1" bigger tube than my Striker. So only 1/2" taller in theory. They put 8" oar stands on the frame. I think my oar stands are only 6" So maybe 2.5" taller than my Striker oar stand to oar contact off the water.
The Slipstream is also 3" wider than the Striker. So 1.5" wider on each side. That's not much of a diff there.
I'm 6'3" with average arms and the 7.5' Cataract KBO 2-piece Oars work well. I've never noticed or thought "These oars are too short." The KBOs are, in fact, 7.5' long, which is 90". The stock aluminum oars that came with my Striker are only 85" long.
Having said that, I trust NRS to outfit it with the correct length oars so if they're putting 8' oars I would think that would be good. If it were me, I'd go with 7.5 based on Gig Harbor running 7s and a review from a seemingly experienced rower complaining about the 8'. But who knows.
The other thing to consider, these boats are meant to get you into tight stuff. Gig Harbor might be running 7s because of tight water. Might be good to ask them why they are running 7s. I know on the upper Klick and Yakima there are plenty of shoots and dumps where my 7.5 oars seem really long. Those shoots where you just have to be going the right direction and then tuck it and go. My 2 cents.
I carry a stocker as spare. I just break it down and it's tucked on the right side of the floor. Never seems to be in the way and can't come undone from the outside or get smashed by a rock.