NO PROBLEM AT ALL WITH THE 61.
I was using Noritake with the 61 and added vm 13......the cte is on the high side with the 61, so I slow cool for 1 min....No checking at all.....I would ideally prefer an alloy closer to 14.2.........and ideally prefer less silver....With over 2 years using Vita vm13, and many years with 900, yet to see any problems.....
With vita, as best as I can remember, anything over 14.4 you need to slow cool.... "Norbert at Argen told me years ago that 61 is ok for Vita."
I will say I try my best to design an ideal framework, be it singles or bridges....
Never waxed badly designed mini pontics with tons of porcelain. But hey I'm not perfect, many times I do under wax.
Always use a non-greening liquid for powder opaques and porcelain with the 61.....and its ok with the paste opaque..........
Feel free to call or PM if I can help.
Charles