I have used my set of wooden planing forms for almost 15 years. Ed Hartzell, the gentleman who taught me rodbuilding, only used wooden forms. Ed built his forms with a 1/4" x 3/4" cold rolled steel strip at either side of the form joint and used the push/pull method of bolting. One bolt would go through an over sized hole in the near side strip and tap into the far side. The other bolt would tap into the near side strip and push on the far side. The system works very will and eliminates the need for inserts and still produces a long lasting form. Place alignment pins a few places along the form joint also to aid in drilling and keeping the form true after assembly. The other thing I would add, is to use hard maple with a very straight grain and assemble the form halves with the grain running perpendicular to the planing surface. The grain is less likely to lift in this configuration.

The photo above shows four wooden forms, left to right (top to bottom) is: Ed's spring loaded form with one screw, Ed's small tip form, Ed's standard form and the tank on the bottom is mine. Mine weights about 30 lbs. and is nice and solid. The picture directly below is the back side of the forms. The next photo is a blurry close up of my form but hopefully you can see the grain running up and down. The second to the last picture is of my steel forms that never get used and the last photo is an end view of a form blank.