I also removed the original engine beds and ground the tabbing smooth in that area.
While poking around in the cabin, I noticed that some of the original tabbing on the main bulkheads that support the mast beam seemed to have delaminated a bit. I really wasn't sure just how extensive the issue was, but I decided that it was best to continue the mess and finish all the grinding in one mega-round than to have to keep making dusty messes. I ground the tabbing in several suspect areas, and in some cases had to grind it completely down to the bulkhead because it was dry and delaminated.
Once all the surfaces are prepped, I'll add new tabbing to secure the joint.