I have done this in my Jeep going up Pleasant Canyon (entering from Panamint Valley) and coming out via South Park. Since I did the whole loop I do not rememeber where it gets difficult. What I do know for sure is that on the South Park portion you have to traverse a narrow bridge that is rated at 6,000 lbs. I saw a Hummer turn around so for sure do not attempt this with your SMB. What is also scary is the sheer drop off and rock ledge on the passenger side as you head down. We spotted each other and it is still unnerving.
I know there are some other tight spots but again, do not recall if they are on the South Park side or Pleasant Canyon side.
BTW, are you located in Isla Vista and is your SMB tan? If so my sister (who now looks out for SMBs thanks to me) spotted a "tan really long van" (i.e. an EB) "with a winch and big bumper" this past weekend while in Santa Barbara.