My 4 year old daughter needs a 3rd seat. She is currently FF in a Britax Marathon in my car, and a Radian 65 in my truck. I plan to keep her harnessed at least 2 more years, then replace those seats with HBBs. Meanwhile, she is starting school and sharing between my truck and my hubby's is no longer going to work. I'm trying to figure out if it would be better to get a seat like the nautilus or frontier that will convert, or go with a seat that is harness-only. She is 39" and 32 pounds. I don't know her sitting height, but she's mostly legs. Are there any harnessed seats that have cup holders? She would adore having a cup holder!