Hi Steve,
You've got plenty of metal there. Remember, there is a bend across the bottom of the panel, and entire bulkhead around the perimeter, and 2 vertical stiffners running the entire height of the panel for the radio stack. The EFIS's when bolted in are rock solid themselves, and even though you have round instruments, there is a lot of metal still left - plenty.
Next...hope you don't mind but a couple of quick critiques.
1) you CB's are too close together vertically. If you plan on using any buss bars on them and even if not, you'll want more room center to center between the rows of CB's vertically. I'd go with wider rows with more CB' and less columns. More Columns mean more jumpers between rows. Less Columns means you can use solid buss bars to gain them together, and there are other benefits as well. Grouping of systems, etc..
2) Why the extra G meter? Assuming you have 2 EFISes, this is a third...just curious.
3) Same with the CDI. The AFS does a better job as an HSI than the GI-106A/MD-200-XXX. You can run both the GNS and the SL-30 into the EFIS. If you're using it as a backup I can understand, but if your intent is as a primary then the EFISes just do a better job.
4) The ADI PII is a great A/P, but with the 430 and EFIS, a Digiflight II would all you to fly coupled approaches, the ADI PII will not. Something I'm sure you've considered but perhaps others have not.
Lastly, you're going to want more vertical room between the jacks.
Overall, an EXCELLENT panel packed with functionality at a great price point. Nice job on the layout, and I hope you don't mind the intrusion of the opinions above (they are worth what you paid for them)!
Happy building and have a great day.
Cheers,
Stein