I’ve not used one fishing, but had one up at full length and it’s a beast with both extentions on. It’s fine at 15 and a bit with one on, but stick the other extention on and you’ll know you’re holding 17m of pole!! Also, as the ‘match’ kit that came with my 774 is more like one of their comp kits, make sure you try it with a power kit to get a true idea of balance.
I had a choice between a 76xl, and a 774, and went for the 774 in the end as it was a more manageable choice. I wasn’t so stoked at the larger butt sections on the 76xl, and the longer sections would have made it a pain.
Not had a z9 up myself, but I would pull the elastic out of a top kit and have them up side by side to decide. Only plus point with sensas, the top kits are very good value IMO. If you mainly fish commercials, stick with the match kits it comes with and take out the number one, I know plenty who use them with double 8 for carp. If not, try and get some swapped to the competition kits (silver writing on black label), they don’t weight any different, and only take up to a number 8 elastic, but they are stiffer than the match kits and I really notice the difference in response times when trying to hit bites from small fish.