My Mruder (bruder cat320 something look alike)

[Lil Giants]

That's pretty heavy! I think most of your problem with surging oil out of your tank is from letting the boom drop too fast (just b/c how heavy the boom is). You could limit valve opening by lowering epa rotation considerably, then you won't have such a rush of oil filling the tank.

My 850's boom is really heavy (didn't weigh it) and I limited the epa on the down to 60% , plus careful control on the tx.

Also, I use Suflo cutting oil from Gunk for all drilling, milling, threading of aluminum, keeps the alloy from sticking/gumming up the bits. I have never broken a 3mm tap, and I use a 18v Milwaukee drill to make a quick job of it.