I'm 5'8" weight 195 lbs. The bike is big, but not too big. It's also heavy, but not to heavy, weighting about 55 lbs. I also ride a 26" (19" frame) folding Montague Paratrooper MTB with a 250w DIY front wheel motor. It's not as big as the Phantom, but big enough. I haven't had any problems transitioning from the Montague to the Phantom. I've done four 15 mile weekend loops through Willowdale State forest and Bradley Palmer State Park in Ipswich. At least 50% on tortuous single track trails, the remainder on double track. I've had no problem pedaling in low gear on flat and gradually rising terrain. I try not to use the power assist when not needed. I haven't fully depleted the battery on any of the variable thumb throttle has three LED lights, green on top, yellow in middle, and red at bottom. At full charge and resting, all three LEDs are lighted. When the green light completely shuts off while resting, you're down to about 50%, so time to turn around and return home to recharge.
I did replace the stock road tires for some Kevlar knobby off road tires. Makes a huge difference in the mud.