That's not a good way. If your mech is boaderline over on capacity then it can rip it off, hence why advice is always the other way around.
There's only so much slack in a chain. Say you have a 40 big sprocket on the rear and 50t up front (unlikely I know, but for illustration) so likely 29t difference in the rear and similar on the front. This would mean that from little-little to big-big the mech needs to cope with 50+t difference which none can afaik. Hence why big-big means this is factored in and if the mech wasn't upto the required capacity then it would just be slack in the smaller cogs rather than taught and ripping the mech off and causing mayhem with everything else. Extreme I know - but that's why big-big.
OK, I assumed the rear derailleur has enough capacity :roll: But with rubez, I should learn not to make such assumptions
what happens if your perfect chain length happens to be two same bits - that the pin can't go through?
No, I like wasting my time as much as you do...