You can fish with the reducer permanently fitted even with the reel up. Just have area at the base of the butt section where the reducer plugs into whipped for about six inches, just like the spiggott area in the middle of the rod. This will provide more than enough strength for even powerful casting.
Have you ever had a spiggott break? No, neither have I.
I personally would still use the reducer, mount reelseat on the very bottom of the blank amd use the reducer as the bit which is usually there under the reel anyway... Then your still gaining about 6-8 inches
having the reel at the very bottom of your rod will make the rod feel softer during the cast, also i cant understand why you want your reel so far down, do you swing it??