Nice work Vader ! My personal distance from home record is only at 3700, although Ive had a few other flights that came very close. Ive only been flying since early august of this year, and I lost my first spark on the second day I tried to fly it, so I proceeded with caution with my current rig (second spark). Going as far as you did in an more urban setting is really impressive. Did you lose signal before the RTH kicked in ? If so ,I am curios how long for ? Since I live in the mountains its pretty easy to get to areas with no interference. Although I dont have the little reflector things yet I still think I could take her over 5000 on the stock setup. In fact your post has me pysched up enough to think about trying it today !
The RTH kicked in on it's own after I lost the signal for about 5 seconds, I was losing it but kept making the Spark climb higher then I'd get some signal back then finally lost the signal and RTH kicked in.