For those curious, mycorrhizae does just fine in the 5-1-1 mix. I recently repotted a number of seedlings started in 5-1-1 and could see the mycorrhizae spores forming a huge web inside the soil around the roots. Additionally, I dug down into some of my 15 gal planters and could see the mycorrhizae surrounding the root ball.

My guess is the 5-1-1 is actually more conducive to mycorrhizae than traditional peat soils due to the improved air/water environment. What's good for the roots is good for mycorrhizae.

Also, I only used Dr. Earth and Jobe's dry fertilizer that contained mycorrhizae, not a wildly expensive special mycorrhizae additive like Great White. Mycorrhizae will naturally reproduce and grow over time so why go with the expensive stuff?