Ok, cargo racks have NO MASS while empty. Now if you're trying to fit a cargo rack on a ship and it says you can't then that's the game telling you that the cargo you will put in that rack will exceed your THRUSTERS ability to move your ship. So upgrade your thrusters then go back to put the cargo rack on then the game won't give you an issue.
Exactly, the biggest problem I see coming from player is the fact that most choose lower grades to improve their range. Which is a good thing if your leaving the bubble, but hauling freight and passengers in the bubble, I've found that more than 20 isn't really needed. A slightly engineered A grade will give one all the thrust and range one actually needs to get around the bubble, where the overwhelming vast majority of player are anyways.
Having a 50 ly jump availibility and being stuck on a object with high gravity, isn't conducive to having a longer jump range. Thus one can install the lesser but rarely utilize lessor size grade between A's and D's to increase range somewhat without actually having to engineer them.
Having a higher jump range than nessasary isn't conducive to anything but long range missions. I've made billions not having done any engineering and having nothing but A grades and being mindfull of my mass when putting on cargo. Where as passengers were never a problem, being able to over load ones cargo carrying ability has always been an issue. IF and when one got involved with a high g of sometime even a two and certainly a three or more.
I've been to thousands of docks on planets since launch, and though I forget the name. I've even landed and took off from an 8 g object (planet or moon). Fully loaded to the max without incident, having nothing but an A graded thrusters and fsd. Though it really does make one slow down and pay attention to their altimeter, rate of decent and speed.
To many player believe that all one has to do is install the lightest engineered to the max module and it will be fine for any event they come accross. Which some times involves being grounded and or a trip to the rebuy screen.
You get what you pay for, A grades cost more than B's and so on down the line, for a reason. Taking a short cut and engineering a lower grade isn't always prudent. But does save one some cr's, until they get stuck. The new system actually helps one to avoid possible issues the player may not have taken into effect becasue of luck or experience of high G objects. We are only aware of the salt they spread here on this forum, I'd assume that FDev gets a lot more reported issues then we are aware of involving being over weight issues.