The Mongoose Dolomite is another decent Fat Tire with dual disc brakes and 7-speed but a small cavity.
You might be able to stick a 2-strike jackshaft in there but I went electric on this one.
3.5" rims and 4" wide tires in the middle.
The 54V 960W 35aH Lithoium Ion battery is in the triangle cavity.
It has a multi-voltage programmable Kelly controller and 24-48V 1680W BLDC motor driving the 7-speed rear wheel.
The Sun rides better, softer tires and better front fork I think, and much nicer handlebars but it hauls a$$ and scary quite.
The discs are pitifully small but that's easy enough to change with bigger rotors.
The Sun is long gone but I still have the Dolomite, putting a bigger controller in it as I burnt up two Kelly's.
Fun bikes no matter how you spin it.
Just make sure you have decent brakes!