Vacuum bagging can replace the need for compression and, squeeze out air bubbles and excess epoxy more effectively than autoclaving - especially if you are not in a hurry. But if you are, the judicious use of a heat lamp (don't melt the plastic bag), or at this time of year- just putting it out in the blazing sun while in compression from vacuum or fixture, can expedite matters appreciably. The autoclaving in a vacuum chamber techniques are required by aerospace applications where preimpregnated sheets, preforms, and many different layers incorperating alternating orientations of filament placement as well as different types of materials are chosen relative to the intended stress load for the finished part. In these applications virtually no cost or time constraints are imposed. This type of work does produce some "magical" part properties that we are not attempting here.
Any way you employ them, just the use of carbon fiber and epoxy is still going to be stronger than polyester and fiberglass/ volume or weight. It would be only worth considering employing additional other types of fibers such as kevlar, (to counter the extra brittleness that accompanies the extra stiffness) if you were not already overlaying some plenty flexible enough fiberglass. As far as incompatibility of materials goes- here in earth quake country (Los Angeles) they routinely wrap concrete bridge support columns with a carbon fiber/ epoxy composite layers to add strength to these structures. Alternatively S Glass enmeshed in epoxy is a cheaper but also stronger (but not as stiff) a combination of even grater compatibility. At any rate, the cost difference is not that substantial if carbon is just used to reinforce local areas of need.
I did not know that the Lola T70 was one of the first uses of carbon fiber in a car. I just got up and checked my T600's composite door (laying on the leather couch next to the Trident)- it appears to be very well consolidated fiberglass matt incorporating strategically shaped and placed foam/ tubing stiffeners. Can't tell as well for most of the rest of the car, as it is obviously constructed from cloth, but I'm not willing to scrape the paint off it or perform a biopsy.
I do remember, however that the GT 40 Mark 2's used carbon fiber in select areas to reinforce their fiberglass bodies. Also of note is the fact that Lola had a lot to do with the developement of the GT 40- so such a claim is at least reasonable. Could be worthwhile investigating how they accomplished this.
