My advice is to use a lawyer specializing in SNT. Also, think beyond the establishment of the trust to who can/will perform trustee duties and where the funds will reside when you die and the SNT gets funded.
When MIL passed away 18 months ago DH and his sister became trustees of their adult brother's SNT. Their brother has physical but not mental disabilities. Due to family dynamics and the complexity of SNTs, DH and his sister were not comfortable performing the trustee duties. We tried to hire an independent entity to take on the trustee responsibilities. Because the value of the trust was considered small (~$200k) we could not find any company willing to do it. Then we discovered a not-for-profit company in WI that specializes in handling SNTs. We hired a lawyer who is on the board of the non-profit and specializes in SNTs. She was awesome but the experience was still frustrating. The way the SNT was originally written, the trustees could not be changed. We incurred legal costs to get the SNT changed to allow the trustees to be modified and make other necessary changes. The name of the SNT had to be changed to adhere to the naming conventions of the non-profit. This also created challenges in getting the Broker to transfer the funds to the non-profit without losing the deferred tax advantages of the IRA and Roth accounts.
When MIL and FIL set up the SNT, I think they were focused on protecting their son's benefits and providing him an equal inheritance. I don't think they understood or considered anything beyond that. If they had, perhaps we could have avoided some of the challenges we faced. However, after much frustration, modest costs, and several months, we now have a situation that is working for everyone.