I would say longer bolts are not needed. Just some finessing and ratcheting and the bolts will sit super snug.All Subarus have a hard exhaust strap connected to the transmissions. When the insert is installed...you pick some engine/exhaust vibration. I run an 85d insert in Frank and I had to put a chunk of rubber between the strap and the transmission to quell the buzz. I have a 3" full AVO performance exhaust...so there is more rumble than stock.
BTW, starting 2010 all Outback have rubber isolators on that hard strap already.
Thank You so much for the feedback
I notice another rumble from the engine at around 1.8k rpm at high speed. So 1.1-1.2k at low speed (city limits) and 1.8k at higher speeds (freeway speed). @traildogck, is there any way to reduce the rumble without taking off the insert? I love the benefit of the insert and it has improved the driving comfort of the car alot (reducing driveline lash and unncessary movement) and I don;t mind the rumble. I'm just asking in case the wife complains about it. LOL