The switches present the same layer-2 VLAN... The idea is to have redundant interfaces into a VLAN. Doing this with etherchannel (F5 == Trunking with LACP) is not a problem. But etherchannel doesn't run ACROSS a switch. Only within it.
Doing it WITH spanning tree SHOULD be possible. But we'd really rather not run spanning tree (In fact we're running with portfast enabled so there should be no STP running).... What I need to know is what's the defined bahaviour for an F5 when you configure a VLAN with two interfaces (Trunked or not trunked) with regards to bridging traffic and ARP responses (e.g. It's defined that you either have a VMAC or the VLAN will use the lowset numbered interface MAC. But nothing says which interface will be used to respond to an ARP request recieved on both interfaces. Neither does anything say what happens if one interface goes down (I'd expect the F5 to just use the other. But I'd prefer it was documented somewhere. (Maybe it is & I just haven't found it of course)).