Hi Peter
Yep, these things can give you a headache when collimating. I could never get the Howie glatter concentric circles to agree with the tak scope. I believe part of the problem is the inconsistent way the laser or indeed the tak scope is held parallel in the 2 inch compression band type focuser.
You can test this by using the glatter spot laser getting it centered on the secondary spot and then removing and putting it back, tighten up three screws in the focuser and the spot has shifted. Similarly if you use the concentric adapter, you'll find it has likely changed its concentricity pattern thrown on a wall.
Off course another problem could be that the centre spot is not truly centered on the secondary!
I also have a hotech advanced laser collimator and it generally agrees with the Tak scope. However once again you might be chasing shadows with the tolerances in the focuser screw pressures. The Hotech is very dependent on proper set up and has more variables to go wrong as compared to the tak scope.
What ever the limitations of the fit and flex in the focuser, the Tak is your simplest and best bet, especially to see any primary misalignment. The tip tilt ring is also likely to be needed to sort out focuser or other axial tilt.
I have also found the slop in the Tak scope needs to be addressed to reduce another source of error. The closeness of fit between the two telescoping tubes is large and this space is filled with a thick grease to slide the focus point. These two sections tend to sag (worse in summer) and this can be addressed with a split collar made from PVC pipe that bridges the two sections and aligns both segments.
I would recommend sticking with the tak scope and many others with RC scopes in the forums would probably echo this sentiment.
One more thing to remember is that further inconsistency may arise from how the CCD camera fits into the focuser. Some in these forums have had made up a direct fitted (screw) adapter rather than using a push fit held by a compression band and three screws.
My 2 cents worth
Ted