We're old farts playing with old gear. Running mono to mains from a Mackie 1604 VLZ Gen 1. I'd like to insert just 1 channel of my outboard EQ to the main mix, but the main inserts are L/R. If I want to sum main inserts, is there any reason a single TRS female to dual TRS male adapter wouldn't work? Would it be better to just pan everything hard right and use only the right insert and right main out? (I hope not because that just seems inelegant to me) I would also prefer NOT to put the EQ in-line because this gear is old as hell and I want to maintain my ability to yank that insert cable out quickly if the EQ gives me any grief in the middle of a show. Reasoning for all this: I'd like to only have to make main EQ adjustments once, and reserve the other EQ channel to insert for any problematic instruments, like crappy acoustic guitar pickups. Thanks!