Another data point, somewhat extreme perhaps. I have 20 year old Ultegra derailleurs on a road bike with 3x10 gearing. Chainrings are 52/42/30 and cassette is 11-36. Using a road link, everything works really well. Chain is sized to allow 52-36 combination without damage, 42-11 still works fine with no slack, and using the 30 tooth chainring, the chain still is tensioned up through the middle of the cassette. The 30-11 combination makes the chain go slack of course, but there is no reason to ever go even close to that gear. So based on my experience, you should be fine with the right length of chain.