Part clipping no longer feasible?

[Captain Sierra]

I tried to recreate my old mun lander yesterday. This involves stuffing two sets of three quarter sized 1.25m tanks under a lander can, radially attached to an I-beam. On physics load, the thing freaked out and exploded because the tanks are heavily clipped into each other. Is clipping dead or am I encountering a unique bug? I should mention this is on a fresh 1.0 install, no mods, no old crafts/saves, no nothing.

[Joseki]

I clipped 2 wings in one fuel tank and nothing happened.