I always go by the rule to not mess with the truck starting battery. This is the only way I can get back home hehe...
Having 200Ah battery capacity from the trailer is alot of power to run your 300WATT Inverters... What most folks do is direct connect the small inverters directly to the trailer batteries and run their home entertainment system from this source.
Your inverter should be connected as close to the battery terminals as you can get them (Typical around 5-feet) and still be inside the trailer. Then you can run the 120VAC extension cords almost any length you need to get to where you want the 120VAC to be at.
This is a typical trailer hookup showing this...
I also would be very cautious what you plug into a MODIFIED SINE WAVE type Inverter. The home entertainment electronic items work best using PURE SINE WAVE Inverters. A lot of dollars are most likely invested in your home entertainment items that might go up in BLUE SMOKE using the MSW type inverters. ALot of others use the cheaper MSW Inverters but I only use PSW TYPE Inverters so that I don't have to worry about things blowing up on me...
Just my thoughts only...
Roy ken
