We did the inverter part of the project on the video several years ago...started with a 1000W MSW unit and after enjoying the system, have upgraded twice to now running a 2000W (3000W peak) unit.
Two rules to follow:
-Keep the 12VDC cables as short as possible (to reduce voltage drop in low voltage lines). Span the distance from inverter (near the batteries) to shore connection with a proper gauge 110VAC cord.
-ALWAYS switch off the on-board charger/converter at the same time as you connect the RV's shore power cord to the inverter outlet (inverter on or not) to avoid the death loop of inverter powering converter, powering the inverter, etc.
Like the video, all our connections are within the RV's outer boundary. For an external shore power cord connection, the connection should be easy to replace with a socket inside a bay (try to make it as easy to access as possible). You can remove and relocate or just disconnect the original and add a socket in a bin. The wires are just like extension cords, but with permanent end connections.
This system provides 4 major benefits over built-in inverters:
-The RV eletrical system remains intact for ease of repair and simplicity.
-Whole house power. But be careful of loading (like NO AIRCON) to avoid damage to the inverter or quick battery drain.
-No complex transfer switch system to fail. The RV just senses the inverter as if it is shore power.
-If the inverter fails (all appliances will fail some day), change/replacement is as easy as a few mounts and cord swaps.
P.S. I highly discourage the use of wood as mounting material for electrical components like shown in the video. If metal mount points (properly insulated) are not available/possible, then try to obtain a poly material similar to a cutting board material. Wood is 1. Flammable
and 2. Can hold moisture which can conduct electricty. Most DIY types don't consider conductivity of wood...but this can cause weird issues in electrical operation, later.