If memory is correct, the SB was to inspect the "inadequate" welds on the gear axle due to failure like this (if I understand what failed on your gear). I would agree the additional weight of bush wheel tire hitting the "Hard" fiber stops could add to the problem but a bad weld is a bad weld. The damage was not just to the axle in past when heavier skies, bush wheels (or not) were installed and the plane absorbed a hard landing, then a very hard rebound against the stop. It could also bend the cabane strut...I've seen several. Someone (don't remember right off) in Alaska came out with a little tube (field approval) that bolted to the main gear leg and cabane strut in the middle to strengthen or keep the cabane strut from bending upon rebound. If someone went to the trouble of selling this mod it happened enough to warrant making the mod. I bought one but never could get it approved without expensive engineering.
I felt there were two ways to fix the problem, first was Tom D's brilliant SGS and the other was lighter bungees. The extremely stiff bungy combo on my 99 did not flex at all unless you hit the ground pretty hard and when it rebound hitting the stops you knew it. The heavier the tire, skies, etc., the more potential damage. I felt a little softer bungy set up along with Tom D's SGS solved the problem. The newer shock dog gear of course helped with this issue and plants the airplane if you plop it in...great change by the factory. Too soft of bungies and you risk hitting the cable stops bending the gear (have seen that too) the other way and potentially the airframe (again my opinion). Also, if you don't mind changing bungees more often, go softer. The correct bungee combo has been debated here quite a bit and each to their own.
As for bush wheel tires. They are not required or really needed in Idaho or anywhere you have an established dirt or gravel strip, provided you stay on the strip. I have seen a plane saved on rollout at Root Ranch going through a 1 to 1.5' deep ditch because it left the runway. If you "need" bush wheels because you land off runway, then you need them. I have them because they keep my prop higher out of the dirt and gravel, look cool, land like pillows and give me a little more protection if I feel like lading off field, etc. They are very expensive and slow the plane 4-5 kts at least but...
The Seaplanes Alaska/Atlee gear are very robust comparing tube size and looks but are a solid 4-5 kts slower uncovered and I think 2 - 4 lbs heavier or more than factory extended gear. I'm not sure if you can legally cover them or if that is an option today? If I'm not mistaken, some of the tire wearing angles have been taken out which I think is a very good thing with bush wheels. The width is a game changer in my opinion on rollout, cross wind and ground handling. The height is nice to. The factory covered extended gear is a little different in that they are actually lighter (I think 1.85 lbs) than the stock factory shorter gear. They are mounted axle center almost 2 inches further forward (not sure I like this) but otherwise dimensionally close to the Sea Planes gear. I chose or had to purchase the factory extended gear (shock dog) this time because they were covered (not much speed loss if any) and legal that way. If you do buy the factory extended gear DO NOT purchase the welded step! I felt it was ugly but I also believe it was in part the cause of a friends gear failure at the welded on step...just my opinion tho. Last time I purchased or priced the two gear, the Sea Planes gear was $4,500 and the factory shock dog extended gear was about $7,000+ covered...several years ago.
Sorry to hear about your airplane but happy you did not get hurt! Just my 2 cents worth of opinions.
Best,
