Softboard size 8ft or 7ft

So I'm planning to buy the following softboard
http://www.ebay.com.au/itm/Billow-7-Soft-Surfboard-7ft-Soft-Board-with-Leash-Fins-Foam-Board-4-Colors-/121251665832?var=&hash=item1c3b2997a8
I am 5'6 , 63 kgs(138lbs) and I'm also a total beginner.
According to the size guide on their ebay page, I should get the 7ft but looking at other size guides on the net they almost always say 8ft is better for my height.
Now I would prefer to get the 7ft because it would fit in my car (biggest reason since I drive a hatch) and I think the eventual transition to a shortboard will be easier.
Do you guys think going with the 7ft will be okay for a total beginner of my size?
Thanks in advance
http://www.ebay.com.au/itm/Billow-7-Soft-Surfboard-7ft-Soft-Board-with-Leash-Fins-Foam-Board-4-Colors-/121251665832?var=&hash=item1c3b2997a8
I am 5'6 , 63 kgs(138lbs) and I'm also a total beginner.
According to the size guide on their ebay page, I should get the 7ft but looking at other size guides on the net they almost always say 8ft is better for my height.
Now I would prefer to get the 7ft because it would fit in my car (biggest reason since I drive a hatch) and I think the eventual transition to a shortboard will be easier.
Do you guys think going with the 7ft will be okay for a total beginner of my size?
Thanks in advance