btw, nuke - I think your marinade sounds good. It's very close to what I typically use - lots of lime juice, garlic, fresh ground pepper, and onion. I don't add salt to my marinade as I will season the steak as it cooks. I have also tried papaya juice (tenderizes the meat very well) but prefer the lime juice. I usually grill the steak before slicing - easier for me to manage. As it cooks, before I flip it I season with salt, and then as the 2nd side cooks I add salt to the top. Slice very thin across the grain.
An aside - I may try slicing the steak first and cook it in the discada over charcoal or a live fire - might be fun...
I am sure some other folks with more experience will drop by with some excellent advice. That's the best part of this forum - we can all keep learning from each other.