This is what I do to start the "what if" process

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iI did this for another member but cannot remember if it was the Vango or another 3 person tent with a similar floor plan.
From the floor diagram I see on the net, the outside dimensions of the 300 are 330x165cm (see under "specifications") .
The drawing is a bit misleading because it seems to indicate the 165 cm to be about 2/3ds along not the widest gap. However if you compare the widest with the 125 cm at the head it will confirm 165cm to be the outside widest point.
That makes the widest point of the inner about 150 cm (the usual gap between inner and fly at the base is about 7cm...
In your case I would spread out the floor of your Macpac and compare it with that....
Franco