Ya the 2stage 8cfm would pull full vac on an oven the size of..... well, a kitchen oven, lol.
A smaller one would have sufficed, but what you will be able to enjoy isn't so much that it achieves full vac, but that it can do so rather quickly.....
I have my tiny lil vac chamber, was using a 5cfm 2stage til the rotor thingy on the bottom snapped... gonna repair it, theres a kit, but meantime I got a 1 stage 3cfm, was amazed how fast and well it works... I think we all preconceive a need for a huge pump.... In reality, for most applications, its just not true....