Thank you for your interest in Sea Eagle Boats. We do not have a Foot Rest for our Explorer Kayaks, however we do recommend that you could use our BOWFLOAT as a foot rest. You can find the listing on Amazon here: https://www.amazon.com/dp/B00RXYM5HC
Depends on what you put into the bag with the 300x, but it would be from 2 to 3 feet by about 12" to 18". Of course, it also depends on how tightly you pack the kayak. It takes a little practice to roll it up efficiently.
The skeg is attached when you slide it into fixture on bottom and set pin. I ussually have vessel in water knee deep and tilt it up to attach skeg as I don't want to risk dragging on bottom hence breaking skeg or fixture. Works well every time.
Thank you for your interest in Sea Eagle Boats. All our Explorer Series Kayaks are rated for Class IV Rapids.