yeah i get what you mean, i get torched for many of my proposed mods from my mates, i guess i'd hate to see you bugger a motor for something that may not have been necessary to have been changed but if you've done your research it should be ok.

i run a winged cast sump on my sr, its a copy of the greddy one that i'm sure has had plenty of r and d done on it, i did as my sump was damaged, i wanted to mount sensors in it which it had pre made and i thought the extra oil would help in cooling.

interestingly enough i've found that with so much oil it doesn't get even close to the temp i want it to thus being a negative thing. so adding 2L is probably going to do the same for you. more oil is not necesarily a good thing, i want more temp and can't get it!