I did not record so I don't know where it hit but I do know that I just miss them quite often and never seem to get an assist. That leads me to believe that my rockets exploding right next to a tank or osti have no collateral damage affect, at least for me
Firstly thanks for the picture complement. Without wishing to seem controversial with respect to your rocket opinion. GV's are coded with track damage. Hence strafing Spitfires being registered for the kill on tanks after someone else really kills the thing. It's in another thread that skuzzy replied to some time ago.
If your not at least getting an assist then I'm afraid to say your missing the target. Near misses will generate track damage therefore giving you an assist. Check that your salvo
DELAY is at default which is .delay 0.05. To much of a spread is akin to firing a single rocket. A line of small explosions. This is why I wrote above about using salvo's. Single salvo for soft skinned armour as you already know. Two salvo's of three (F6f) on moving heavy armour and salvo 5 on stationary armour.
If tanks can richoshay rounds off one another I don't see anything unusual about rockets richoshaying. After all they are smaller in lethality than a tank round. All I could recommend is perhaps a sharper angle of descent.
Rockets don't seem to have a set convergence. You just aim a little left or right depending on which one fires off which wing. I use this method for Gv's only since most other targets are larger. Great pics Lynx
Personally I aim at the target as seen in the "aiming" screen shot above. However, if aiming off either left or right is working for you then that's good. May the force be with you