Advice on using a rigid insert/orthotic in climbing shoe

Would like advice on using a rigid insert in a climbing shoe for 1st MTP joint pain. I have been using a carbon fiber Morton's extension in my street shoes (the ones that can accept an insert anyway) but it is too large for a climbing shoe, and I am not sure if it would crack eventually from the forces generated in normal climbing technique in the foot. To be more clear, I have not been diagnosed with hallux limitus or rigidus - just some unspecified injury that's been going on for quite a while with a long, gradual recovery (yes I've seen a doc). Wondering if I can ever start to climb in a climbing shoe again, but it seems a rigid insert would be the next step to protect the joint if I did.

What have you used and how small did you size down on the orthotic? (I know this is shoe dependent but let's just say it won't be going into extra small, aggressive shoes....) 

Thanks a ton, Dana! At least it is a starting point. It wouldn't be "forever" use (as far as I know), just something for a while to protect the joint. Also, the price is good. I spent about $70 on the carbon fiber insert, but I usually only buy from a certain online retailer which I trust, and they are not the cheapest. 

keep us posted.  i am pretty curious how it works.  my dr just diagnosed me with bilateral halluxus rigidus on both of my big toes.  currently starting a bunch of physical therapy.  my PT seems like he would like to avoid using restrictive items (ie stiff orthotics, etc) and try to get more strength and flexibility back.  it will be interesting to see if it works, or if i will need to try more of a stiffening/support approach.

Important: Hallux Limitus/Rigidus (literally "big toe stiffness/rigidity") is a symptom.  Generally arthritis caused by an injury or bio-mechanical issue.  What has worked for me or someone else may or may not work for you.

I have Hallux Limitus/Rigidus one one side.  First symptoms appeared without any identifiable mechanism of injury - most likely hereditary.  Cheilectomy surgery ~4 years later when pain became so severe I was limping all the time.  Joint surfaces intact but post-surgery ROM was and is significantly less.  Very long recovery period with very gradual return to climbing.  Almost flat rigid CF insole in climbing shoe on affected side, and toes must be completely flat.  Toe is often still sore after long days of activities such as climbing and hiking.  Recently I've been able to forgo the CF insole during gym bouldering sessions only - first time in 6 years. 

Standard treatment (regardless of surgery) frequently includes wearing very stiff and usually rockered shoes.  They actually cause me even more pain.  I've determined through experimentation that the issue lies in the usual forefoot upward "pre-curve" of the shoe, which always keeps the toes flexed.  Most shoes have this "pre-curve" but the stiffer the shoes, the worse the effect is for me.  Walking in stiff cycling shoes, even less aggressive "touring" models, becomes painful quickly.

Altra shoes, including their casual models,  are by far the most comfortable shoes for me.  They have zero-drop (less loading of the toe area when standing), limited "pre-curve" in the forefoot, are very flexible, and are quite rockered in the more cushioned models.  It's pretty much all I wear now.

Secondary issues to be aware of: Hallux Limitus/Rigidus can affect your gait which can negatively affect your knee(s), hips, and back etc.

Ask gblauer. Her late husband made her inserts for the climbing shoes, after she had ongoing pain that wasn't fixed by surgery on her toes, if I recall. My memory is hazy, it's been a long time since she posted about it,