I misjudged a surface approach last night* - wasn't paying enough attention, esp. to the gravity - and almost destroyed my
DBX**. Took out the shields and left the hull at 20%.
Hadn't boosted, but realised a little too late that I wasn't approaching in a gentle/useful "boop the nose" kind of lithobraking fashion, but more of a non-gentle "crunch"; possibly worsened it by pulling up the nose just in time to belly flop. Doh. (I didn't record it but I think I hit at "only" 250 - 300 m/s.)
This got me to wondering about how the shield and hull are affected by impacts and that led me here...
I was convinced I had read somewhere that hull reinforcements didn't help with impacts (or some kinds of impacts?) since certain damage is proportional to the hull strength, but this thread suggests that actually HRPs do help with collision damage so I have presumably got that mixed up with something else. There's also a hint above that belly flopping might make it worse - is that the case? Pointers welcomed.
As for shields, is there a way (other than experiment!

) to guesstimate how much you need on a given ship to be able to smack into a planet at say 300 m/s and not take it down?
[* I was approaching an "impact site" at the time, for added irony

]
[** My DBX has a chequered past so it's a rather weird build that I should redo at some point. Started life as a bubble taxi (early in my ED career, so limited engineer access), then had adjustments for various other tasks, including mats gathering, light exploring, and most recently jumping around for ground missions and searching for pre-upgraded kit. Am pondering Dolphin and Krait II for doing a better job on the ground mission stuff.]