Check out the forums on Surfski.info for surksfki specific forums.
I have a gen 1 Stellar SR for reference and have had tippier boats in the past, but got rid of them to better learn my wing paddle stroke, and as Oscar says, Stability Before Ability
Anyways, the general consensus over at SS.info is that for novices and even lower intermediate paddlers, the speed difference between boats below 6 mph is negligible, as most of the resistance is from hull friction, not wave resistance. Therefore, unless you can paddle above approximately 6mph for about an hour, there is really no benefit to a skinnier boat, speed wise at least.
Also, there may be a large detriment to a skinnier boat, that is, if you are bracing, you’re not padding forward as fast. If you’re concerned about stability, you’re probably not focusing on technique, leg drive, torso rotation, ect. Also, if you’re apprehensive about stability, you probably wont take the boat out in conditions it was designed for: WAVES! ohh god riding waves are fun in a ski. Im inland and rarely get to the ocean, but even chasing ski boat or fishing boat wakes is fun.
So my .02 is for the V7 for now. Paddle the hell out of it for a year or 2 and upgrade to a 19" ski when you want more of a challenge.
For me, I have decent natural balance and could handle the SR in all but the messiest conditions right off the bat. I am ok with the occasional unintentional swim, and I often paddle 3-4 days a week, so balance improves with frequency. Decide how much of a challenge you want (balance wise) and how much seat time you can put in. If you’re paddling less than 3 times a week, get the more stable boat to start and focus on technique, technique, and technique.
Ask the same question on the surfski forums and you’ll get more experienced paddlers answering as well.