Acoustic Guitar Construction

I'm working with a set of pre-bent Martin IR sides purchased from a 3rd party and using the LMI 14-fret OM template with the KMG mega mold. My question / problem is that when I put the rims in the mold I have a roughly 1/8" gap near the narrow portion of the lower bout on both sides that spans roughly three post-lengths on the mold. I've tried every possible configuration with the spreaders to try to alleviate the gap, to no avail.

One thought I had was to add an additional spreader between the sides at this point to gently try to force them out to make contact with the posts prior to proceeding with the rim construction. Is this a good or bad idea? If good, should I fabricate and install two more spreader arms in the mega mold like the others, or consider just using one of my longer turnbuckle spreaders?

Or should I just live with the shape and the fact that either the rims relaxed a little before I got them or they were originally bent to slightly difft specs by Martin than the LMII template I'm attempting to use, which I chose because it seemed to have the closest plan to the earliest '29/'30 OM body I'm trying to build. But then if I just lived with this difference in shape, I guess it would be crucial to take exacting measurements of how much I move in each side's corresponding posts in to meet the sides in this three-post span, so that the sides are mirrors of each other as they should be. ?

Any help or advice would be greatly appreciated. Maybe I'm missing a better solution. I've attached photos for reference

I've done both of the fixes you present. I've used additional spreaders as long as it is not too much force. I've also adjusted the mega mold to match the new contour (one benefit to the adjustable mega mold). You just want to make sure if you adjust the mold that it's equal so when you flip the rim back side down it fits.

Looks like the waist curve was not set and it relaxed. Either solution will work OK (re-bending is the real cure) what ever you do (as John mentioned) try and make sure the mold halves are symmetrical. Make a half pattern from your LMII template, you may be surprised to find out that the template itself is not symmetrical, I believe LMII mentions this in their ads.

Thanks for the good info here and the quick responses. Big help! I will post a follow-up with the solution I opt for once I address this issue. Happy 4th of July wknd!

Because I don't have a bending iron I ended up opting to add additional spreaders to press the sides against the 2-3 posts of the Mega Mold on each side near the top of the upper bout where the rims had relaxed, creating a roughly 1/8" gap tapering down over roughly 3" long each on both sides.

I fabricated two 4" spreaders and two risers out of mdf similar to those already incorporated into the Mega Mold and located them with 2 1/2 lag bolts and wingnuts in the area where they could best help close the gaps.

This mostly solved the problem--now I'm only contending with about a 1/16" gap out from just one post, and it's equal on both sides, so having made sure that my template and the corresponding post locations are identical on both sides of the mold, I'll likely just adjust the one post in that 1/16" on each side and live with what will be a near imperceptible difference in shape from my original template.

I've attached pics of the mold with the additional adjustable spreaders and the rims now trimmed and in place and ready for the next steps. We'll see what if any complications arise out of this. Thanks again for the feedback.

I really hate jamming the rim into the mold (or force fitting any part of the assembly for that matter) --- I still suggest that you make a half pattern that fits the sides as bent and set up the mold accordingly. Have you taken the time to inform LMII that they bent the sides wrong -- which is the real issue here.

I am sorry -- I just re-read your post, did you find out which profile your (3rd party) sides were bent? LMII sells two OM style templates and neither one matches the actual Martin shape. So its no wonder you are having problems.