'AWS PCluster - create CloudfFormation template

After creating a new AWS Parallel Cluster, I'm getting the error The following resource(s) failed to create: [MasterServer]. from the CloudFormation logs and terminal.

The issue is that I have a post install script that takes around 1.5 hours to complete. It does complete, but the PCluster status is CREATE_FAILED - - AWS::EC2::Instance MasterServer Failed to receive 1 resource signal(s) within the specified duration.

So I know that I need to modify the Timeout line from the default CloudFormation Template to PT130M,

Resources:
  MasterServer:
   ......
     CreationPolicy:
      ResourceSignal:
        Count: 1
        Timeout: PT130M

I've uploaded that file to an s3 bucket with public access, and specified it as the value for the template_url parameter in my pcluster config file successfully. The problem I have now is that there are a whole lot of other parameters needing values in the template_url file which I believe are populated behind the scenes (or atleast are not explicit in the pcluster config file) with pcluster create.

Is there any way to get/find the CloudFormation template created from the "failed" cluster to pass as the tempalate_url in the pcluster config? Is there a way to only update that one value (Timeout) in a CloudFormation Template, while keeping the rest as default?

I did notice there was a recent commit to PCluster v 2.11-release with a modification similar to what I need, but I'm unsure how to go about using that source code in my local Parallel Cluster. Also, not even sure if that would work, as I need around 1:30 mins of timeout.