I lay mine flat, and it really isn't a huge deal with the Pioneer.  It's mainly when I'm really tired at the end of a long day, and I don't quite lift straight up, a strap or buckle might catch on the gunwale and make me lose my balance...
I have never packed the pioneer completely full while on a solo trip, so I am sure I could get by with the smaller Explorer.  My second pack is the Rucksack, and it is really nice as my single pack on day trips, and fits well in the bow.