For my 2pence worth as an automotive structural designer, there are two options, a, do you wnat the tree bars to be absolutely solid and assume they are just tree bars, or b, are you looking for some deformation inan impact to prevent the full pulse from being passed onto yourself.
Due to the nature I would assume 'a' is the direction you're aiming for in which case I would go with the first of your two sketches but would make use of some tubular front shock mounts which would attach to the two upper bars and down to the chassis, with the shock mounts suspended bellow the cross brace between the two top bars.
If you wanted to go the whole hog and get a little indepth I could model the options in CATIA and run them through the analysis program to let you know which performs better. ( the more technical version of Simon's straws )
I would be tempted to look at the Raid Rally cars for their bracing ideas, Tomcat ( obviously my personal favorite ) and Wildcat pictures are all over the net, but if you can't find any I can get a wing on the Tomcat and take a picture. It is more simple than my suggestion and still incredibly robust, just the fibreglass which lets it down.