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In the meantime just use more trim for rotation

No problem at all  ;)


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full spoilers in flight breaks almost nothing

Sorry, my native language is spanish. I'll try to explain again.

In another similar plane, at 300knots if you put spoilers full extended for 5 secs, it reduce speed to aprox 270 knots. You "feel" deceleration. The VC moves a lot.

Now, in same situation with 727-100, after 5 secs it reduce speed to only 293 knots. VC moves just a bit giving sensation of not "feeling" deceleration.

Doesn't happend to you?


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this will never be perfect as the trim needs to be set according to a chart based on the percentage MAC you have when the aircraft is loaded. Ideally we would have a utility to show this value after loading the aircraft

Well, I use a program to read and write values to FS (because I've build some basic cockpit parts). Because of that I'm able know almost all information needed :). FSUIPC has a variable for that:
Offset: 2EF8 Length 8
CG percent, as a double (FLOAT64). This is probably the position of the actual CoG as a % of MAC.

If you want this program I can point you to it. It's free for home use.