Final answer:
The question is related to an engineering principle, but lacks enough information to determine the exact length of plastic tubing for a hook blade knife. It seems to be a question better suited for a specific product design query, rather than a general physics calculation.
Step-by-step explanation:
The question you've asked appears to be related to a specific application that would typically fall under engineering principles, which includes aspects of physics.
Unfortunately, the information provided is insufficient to determine the exact length of plastic tubing that would be installed over the hook blade knife of the pocket assembly. Usually, such measurements are determined by the specifications of the project or the product design. In the information provided, however, there is a mention of general rules of thumb for spacing and depth, which are not directly applicable to the length of tubing on a knife blade.
In a similar context, the overall IMA (Ideal Mechanical Advantage) of a wire cutter, as described, could be calculated using the distances from the pivot points to the effort and the load. However, this scenario doesn't provide enough data or context to calculate plastic tubing lengths on a blade.