Cutting rectangular ductwork requires careful measurements and the right technique. Use a measuring tape and pencil to mark the cutting lines accurately. Tin snips are excellent for straight cuts on smaller ducts. For more extensive or thicker rectangular ducts, a reciprocating saw with a metal-cutting blade is effective. 

Ensure the duct is well-supported and secure while cutting to prevent wobbling and maintain precision. After cutting, use a metal file to smooth any sharp edges, ensuring safety during installation. 

Sawing your hot tub into more manageable chunks so it can be lifted easily into a truck takes several hours. Generally, 2.5 hours for smaller hot tubs and around 4 hours for larger ones with the help of one to two people. If money isn't a concern and you want to skip the physical labor, you can hire a pro to get the job done.

You should not do your own welding unless you have the proper training and experience. Most home electrical systems can only handle MIG welding, which creates weaker bonds than TIG welding and won’t work on certain metals or metal thicknesses. Both welding forms usually require the use of shielding gas, which can be dangerous to store at home. Additionally, welding machines create temperatures of over 3,000 degrees, and the sparks can blind you if you don’t have the proper equipment. As such, it’s usually better to hire a professional welder for your welding projects.

Professional metal fabricators typically charge around $70 per hour, but the total cost of your project will depend on several factors. The largest cost drivers are the size, complexity, and design of the project, as well as the price and type of metal used. A good way to estimate the total cost is to multiply the cost of raw materials by four; typically, one-quarter of the total goes toward materials and three-quarters toward labor. Your geographic location can also influence costs, as labor and material prices vary by region.