Although a low break vs radar missile is realistic, would it have any real effect in FA? does FA model missile energy vs altitude??

Sounds good. It seems like during campaign play, I have to tell my wingman to maneuver while the enemy can just pop 3 chaff and continue to fly straight and level, defeating my missiles in the process.

I always figured they built in a cheat to make up for the AI enemy never using jammers.

You can model missile's loss of energy by having reduced turn rates when unpowered and performance reductions down to sea level. Its a graduated decrease from the performance level you set at 20K ft... Lets say in this example you make a missile that has no performance reduction at 20K ft, you can set it to have a 50% reduction at sea level. It will have a fraction of that reduction for every 1K ft of altitude below 20K ft to your sea level reduction. So at 10K ft the missile has 75% of performance vs 20K Ft and if you set the unpowered turn rate to be a fraction of the power rate(again say 50%) then the missile will not only have a reduction performance as it drops after you in altitude, but if it runs out of fuel it will also have an even further reduced turn rate against you in this example...

You also have other Hit Modifiers such as Increase to performance whenG's pulled by the missile is under 3G and Decrease in performance when G's pulled are over 3G, thus adding even more limitations to the missile's performance if you jink hard and drag it down in altitude...

And an increase in performance for the missile's radar seeker if its a big target like a transport or a bomber which cant maneuver as much... You can also set the maximum G the missile can pull in the final 2000 ft before it can hit you.. So if the missile is pulling 20Gs and is within 2000 ft of you its likely going to miss if you set this limit to 20G. All my SAMs have this set to a specific limit for their final G pull as they are almost always unpowered when this occurs and if you jink hard enough you will make them miss you...

Also you can set deceleration rate when unpowered and make it respond to gravity when unpowered and set it to compute target lead so its not always a tail chaser. I just recently discovered this option and enabled it for my SAMs so they now fly a lead intercept... But it only works if you set the guidance correctly or else the missile will not function.

Also you can add Doppler parameters so the missile is vulnerable to "notching" by making a whole where the missile can not locate you if you fly perpendicular to its trajectory at sufficient range. This needs to be set to correctly mimic "notching" to be used against an AI bandit or it will track you with its weapon's seeker head if it loses you with its own radar...

Have you found a way to calculate turn rate for SAMs?
The defaults for FA are pretty off and I've been able to find, largely, what missiles can do as a max.
However converting that into turn rates in the FATK has been a bit troublesome.

In past I just used that # so if a missile could turn at 18g I put 18 in there.
However, I think I am understating their agility since in the FATK this # is degrees per second.

I've found some formulas online for converting but I don't really get useful values.
Based on documents I see a rate of turn formula being: (1091 * tan(bank angle))/velocity in kts

So for Mach 4 turning at 90 degree bank angle. I get -0.94 so clearly I'm doing something incorrect but that being said even this formula doesn't seem to give me good data when I look at what few charts I can see.

Why would you increase the turn rate to twice the maximum G? The Max G means that the missile can not exceed that G no matter its energy due to its design...

In the FATK the turn rate is deg / sec I haven't been able to convert from max G to deg / sec.
That's what started my post there. I think the turn rates are too low using this method.

You have to reduce the turn rate and increase the drag and decrease the number of G a missile can pull by an exponential factor below 20K feet to replicate the effects of denser atmosphere. Unfortunately there is no formula. You have to test it out manually after changes to see if you can out maneuver the missile at lower altitude if its possible to do so in the real world.

All right wound up doing some testing on this too last night. Push comes to shove, I used DCS as a model and in DCS I found a video someone posted of defensive maneuvering to drag missiles down but unlike most of them it went into more of the science of it versus just the maneuvers. It even included a little chart of DCS ranges of missiles. What DCS does is simply match air density. At 20,000 feet vs. sea level, the air is 54% less dense. Comparing ranges on that chart you see that at sea level, the missile has 46% the range it does at 20,000 feet. Simple enough really. So I'm going to use 46 for a sea level modifier and 100 for 20K.