That’s reasonable, but in my 30 years or so messing around with modding, motorsports, and aftermarket parts nothing ever goes exactly as planned, that’s why there is a difference between OEM and aftermarket.
With OEM parts tens of millions of dollars are spent in R&D and tooling to get a well fitting part for the masses, but being designed for a ‘baseline’ of consumers many people like to operate outside the baseline, or need to.
Then the modding with aftermarket parts begins. Now you are into short run or sometimes even “one off” parts that are customized to you, those are NEVER long run consistently produced parts, they simply can’t be because they’d have to spend tens of millions of dollars in R&D and tooling in most cases to do so.
Simply put, 100% of the time there is going to be a gap between what is and what’s supposed to be. If it’s a high quality aftermarket short run or one off part that gap will be small, if it’s poor quality that gap will be big. Either way, 95% of aftermarket parts I’ve ever bought require at least a little bit of ‘fiddling’ to get right.
Your PERSONAL tolerance for fiddling to make it work is going to determine a lot of how well you like a part and get use out of it, this is what I was referring to when I said 90% of the people here would have had that seat on in ten minutes and moved on with life lol
If you have ZERO tolerance for fiddling to get something right you should either have your shop do it for you and move on, or only buy OEM.