Pre-laminating transom core?

[gw204]

Guys, I figured I could save myself some time on the transom project this fall by going ahead and laminating the core (whether it be Coosa or marine ply) over the summer. Then when the time comes, just make a quick template and cut the whole thing to size and glass it in. Being the inexperienced glassman that I am, I figured this would allow me to take my time (figuratively speaking) and decrease the risk of poor lamination. I wouldn't have to worry about hopping in and out of the boat, I could drill all the necessary holes to thru-bolt ahead of time, etc., etc.

Is this a definite no-no?