Hi Les
Check the physical interface of the Tak Extender. I have the Tak x1.6 Extender for my Mewlon 180 and as you can see in the attached photo, it has a raised glass element at the “camera” end of the unit.
I have found that all my Tak accessories have a well-designed and solid physical interface with each other, which makes sense as I guess that they are designed as an overall, integrated system.
The 3rd party Barlow’s may well be as good optically and will likely fit physically, but the metal work, cut outs and locking screws on the Tak accessories are all solid and match each other which is a nice feature.
I also have a Tak x0.8 Reducer and I find that it does not sit well with some non Tak accessories, in particular focusers that have a brass compression ring. The ring does not clamp the Tak barrel securely due to the machined design of the barrel of the Reducer. My Tak Extender has a longer 2” insert so does not suffer from this problem.
I also have several TV PowerMates and they are excellent optically and mechanically but not designed specifically for the Tak idiosyncrasies, which may or may not, be a problem.
Cheers
Dennis