I've been flying this zagnutz 52" wing for quite a while. I recently added the fuse underneath to house FPV gear. I believe that I have the CG set as before about 7.5" from the nose of the wing. However ,under power it flies okay but with little elevator authority and with the motor off, it wants no nose down hard. My question is this. Would adding this fuse require me to move the CG in relation to the wing? My initial thought was that the CG should be in the same location whether I am flying with the fuse or without. Could be totally off base here though.

Thanks-

I'd love to know the answer to this as well.
I've been scratchbuilding for a little while now, but have yet to have a successful flight. But from what I've learned so far I'm starting to gather that CG placement is mostly related to the type and shape of wing. Your experience would seem to suggest otherwise.
The other rule of thumb I think I'm starting to see is that a proper CG should give a nice glide from hand-toss with flat stall. If it wants to nose dive hard then I need to pull the CG back.
Would be nice to have some easy guidelines to follow as this is starting to seem like quantum physics!

With some fuse yes. Because the fuse can potentially provide lift and should be considered as part of the wing. But this should only affect "flat" fuses like the real life SR 71 Blackbird or the StuntCat RC model.

For your fuse it shouldn't affect CG. However, you are adding quite a lot of side area ahead of the CG while having very little side area behind the CG (your tip fins). This reduces lateral (yaw) and spiral stability. From the point of view of the pilot, the plane flies perfectly well in a straight line but try to turn or roll it and it misbehaves badly to the point that controls feel "mushy". That's basically your plane wanting to enter into a spiral dive.

I suggest increasing the size of your fins and extending it back a little beyond your wing's trailing edge.