I work on mine when I have time and lately that been sparse. Here are some tips that might help you, just bear in mind I am talking about my kit, each will vary slightly.
Regards to inlet of lock. On mine all I did was dissemble lock then file a slight draft on the plate. I kept filing the plate until it fits the mortise, don't let it fit tightly or you might chip the wood taking it in and out. Also when you finish it the finish probably will swell the wood making it even tighter.
Then assemble the lock and put some inletting color (I use Prussian Blue) on all the parts that might contact wood. Put the lock in and tap it lightly so the color will show where wood/metal contact. Pull lock, relieve wood where contact was made and repeat until lock is against barrel and operates without binding on any of the wood. I had very little to remove.
Trigger plate needed a little relief of wood in the rear to make it fit perfectly.
The only problem I ran into with the triggers were the top of the trigger bars were contacting the sear bar. I removed about .050" off the top of the sear bar and that took care of the problem. With the trigger bar screws and in place make sure you have a little space between the trigger bars (both front and rear) You can test this by moving unset trigger back and forth to see when it contacts the sear bar. Mine had no play and just touching unset front trigger would trip the lock.
Oh, one more thing make sure you file enough draft/metal off the sides of the tang that it will easily slip into the mortise. Also be sure to draw file the barrel before you force it into the barrel channel. If not you will have
lots of fun taking the barrel/tang in and out of the stock. You do not have much wood in the forearm to man handle pulling a tight barrel/tang out of the stock
Hope this all makes sense.
Dennis