Yeah Celigo is working fine for generating IFs in bulk. Im just mainly concerned with performance issues on the record itself.

Do you only dispatch/ship 1 truck per day?

Not really. It can range depending on the speed they get loaded and the weather

I'm unaware of another unit of measure greater than MT; with those quantities, you need to think of a way to group shipments (trucks, in your case). If you don't need to Invoice them daily and per truck, you could build something that groups several trucks before it creates a fulfillment. Not sure if you will find something out of the box to do this, my educated guess is: no, you will need to build a custom solution.

Yeah its been a fun/challenging account. Currently they use the Item Fulfillment as a Trucking ticket. The trucking company then sends a bill containing the IF# which then allows us to keep track of the trucks we pay and make sure were not overpaying the tucking company

You should be able to offload that logic to a custom record and do some custom grouping. But if all you care is to be able to see the related IFs, then you can probably get away with a custom sublist and summary search, otherwise a custom Suitelet that serves that sublist asynchronously with something like datatables or something like that.

The custom record is where I'm leaning too. The last thing I want is the Sales Order Record to seize up. Always something..