If I have to carry the weight of a 7900 I want it to have 79cc not 64cc.
I agree, but if you're not carrying too much, the 6401 is waaaay cheaper than a 7900 and is adequate for most uses. The 6400 would be under $500 shipped, while a 7900 in these parts is around $800 otd. And, if you really need the power later, spring for the OEM 79cc jug for less than $200 and you're still ahead.