Boy, have you opened a can of worms. Checking problems usuallly stem from too short a tail (.9" or less) and tail radius too small (3" or less). Get yourself some thin, narrow hardowwd and some thick CA and glue on some textendors to the current tails. Set up a piece of wood to fit the slot of a disk sander and fasten a piece of thin stock, 3/16" or so and put a nail in the stock about 4" from the disk. Use the nail as a pivot point to re-radius the heels. CLean up the sides and you have new tails. The other problem is very likely geometry. First check the distance from the hammer shank center pin to the wippen flange center pin. This is best done with a digital caliper. The spread action should be 4 13/32" or 4.440". You might try slipping a 1/16" shim under the upper lobe of a wippen flange and regulate that note and see if that works. ALso check the location of the capstans on the wippen custion. If the impression is toward the back of the cushion the capstans are causing the wippen to travel too far. Even if the capstans are centered they may still be mis-located. Relocating the capstans is a tricky deal if you don't have the right tools; digital gram scale, set of key weights the the new metrology of David Standwood. If the shanks have been replaced from the original there is likely a mislocation of the knuckles. In this case checking several different chanks will help you decide which knuckle specification to use. Others will have more ideas as well. Best of luck.
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