You really can't go wrong with either the 8" or the 10". Given that you'll be hunting a lot of beach and won't be encountering a lot of surf & currents I'd get the 10" for the added coverage. The 8" is more of a utility coil for trashy areas, uneven ground, or when needing to reduce the amount drag on the end of the shaft, etc. Since you shouldn't be encountering too many of these issues I'd go with 10". However, eventually you're going to want to relocate/balance the weight on the shaft as swinging the Excal in it's stock setup can get fatiguing due to all the weight in front of the hand, this will also add a lot of drag when water hunting. There are several post in these forums in regards to balancing the shaft that you should probably be looking at because sooner or later you're going to want to balance the shaft.
Go with the 10 inch, you want to cover as much beach area as possible with each swing, your not going to run into that much trash at most beaches to be worrried about it... I have modded my excals, one has the 15 inch wot coil, another has the 12x15 inch SEF Butterfly coil. I use both of them in the surf and swing them for hours, granted I am only 64 so age is still on my side....
Go with the 10 inch, you want to cover as much beach area as possible with each swing, your not going to run into that much trash at most beaches to be worrried about it... I have modded my excals, one has the 15 inch wot coil, another has the 12x15 inch SEF Butterfly coil. I use both of them in the surf and swing them for hours, granted I am only 64 so age is still on my side....
