This seat was made by someone else but I am working on a few changes to the seat. However, it consists of multiple parts. I would like to mirror this, but using the plugin removed some details of this seat meant it does not look accurate.
I have attempted to use Blender but since this consists of multiple parts, it seems to be taking some time to mirror. I was not able to change the colour of different parts since it randomly exported the whole thing.
You can try to do it the old fashioned way by rotating the item 180 degrees and move the stuff over to the opposite end.
I’m serious, this has worked for many in the past and is still effective today for builds that aren’t complex. I would suggest however that you try to union the seat and add the texture again, and try mirroring it once more if you haven’t done so.
The only way (in Roblox) to reflect if you can’t just reflect using the reflect tool and then rotate the unions around is to separate all of the unions into parts (and negate parts) and reflect it using the tool and then re unioning all of the parts.
I have decided to try a similar method to yours by seperating everything until it becomes a part then reflecting it. It has worked and I’m happy to say I am finished with reflecting the model. Thank you.