I have only placed down one shaft But the bugs never tried to come up through it. I haven't dug very far at all and only had 1 biter base spawned within sight. Was eating 8 UPS of Pathfinder. This was after i had console commanded all of them on the surface away. Not sure if there's any fixes other than disabling bugs entirely but I'd rather keep them if at all possible. I rather enjoy the concept of extra danger while mining. If you have any tips on ways to keep the biters below from chewing through my UPS I'd greatly appreciate them!

see nauvis-underground bad efficiency branch.

my emergency solution (i use mod blackMarket):
switchOn debug, show chunk activity, pathFinderRequests.
then build 9 artillery with arm aim into underground. bombing nests and bitters into active chunks (i use acid ammunition). repeat while pathFinderRequests on map !=0 and Active chunks (in black zone on the map) is exists (>2).

Sorry all I have been really busy and a little tired. have some time off so going to try put in some limits on biters and nests next couple of days

Sorry all I have been really busy and a little tired. have some time off so going to try put in some limits on biters and nests next couple of days

thank you for supporting the mod at all and not abandoning its development.