Frame boxing is a surefire way to get it so rigid it cracks. We finally decided to bolt on everything except the roll cage after many years of patching stress cracks on the dirt track cars. We needed enough rigidity so spring rate adjustments would result in predictable handling changes, but the frame needs to flex a little on a street machine. Going from full throttle to idle several times a lap with a 600+ HP engine on a surface that resembled a motocross track after a couple of heat races had a habit of finding the weak spots.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!