ORIGINAL: BFoote
There is a reason that all delta wings have their tips set so that at cruise their wingtips provide NO LIFT and in fact generally provide negative lift. It ain't for high speed performance either. Its called low speed control performance or lack thereof and maneuverability.
I'm a model airplane flyer and I've been bringing scratch built flying wings and deltas out to the field for about 25 years.
I've also been approached by guys like you for the same amount of time, with all of the typical wive's tales and myths that do not pertain to an intelligently engineered flying wing/delta model.
Long story short...get yourself any engine from 1 cc to 6.5cc, then do your level headed best to build the fastest delta/flying wing you can, then look me up for a speed contest from hand launch to touch down.