I am trying to optimize a simulation model for speed so I can run through multiple design ideas fairly efficiently.  My assembly is made a some thin walled solids so I converted those to shells.  However, I am finding the calculation takes LONGER with the SHELL and SOLIDS, than than if I just left them all as SOLIDS.  I was always under the impression that using shells would increase model speed.  Instead, it seems like there is an additional step called "Forming surface-to-surface bonding" that adds to the overall solution time.  Any thoughts?

Shell/Solid model

DOFs: 194,994

#of Elements: 27,712

#of Nodes: 56,655

Solution time: 00:02:30

Solid model

DOFs: 292,566

#of Elements: 48,919

#of Nodes: 98,128

Solution time: 00:00:32

(I'm running a fairly coarse mesh just to baseline the speed of the new model)