Man, if you're not carrying tent, sleeping bag, mattress and other camping gear you shouldn't have any problems. I have a Lowrider with detachable bags and a smaller Tour Master bag that doesn't extend above the sissy bar. I also carry several bungee cords and a small bungee spider net.
I'd probably carry the same stuff that I'd carry for 5-6 days. Anything over that is just washing clothes, not needing more. Staying in hotels really lightens your load. Most hotels have overnight kits (or individual toiletries) available free for the asking but I don't see you really needing those 'ceptin' you pay for those in the price of the room. Rinsing socks in hot soapy water at night works well for me and they're dry in the morning to wear again. Cleaning clothes is your choice, rock in a stream, drop off at laundry or sit for a couple hours in a laundry.
I'd probably carry more clothes than others because after eating road dust or sweating most of the day I need to sometimes feel clean. Also I don't want to waste time washing clothes everyday. Staying in hotels there's just something wrong with crawling out of a shower and into smelly clothes. But that's just me.
I'd pack;
3 pr jeans (and wear a 4th),
3-4 T-shirts (gonna buy more),
4 pr socks (couple of good padded, wickable boot socks, couple for walking and wear a fifth),
bungee a jacket that can live in the hotel if not needed,
comfortable shoes for walking (like running shoes),
several throw away plastic razors (hotel soap for lather),
couple of bars of hotel soap (whenever I stay in a hotel I steal the soap daily so I have a stock)
large, good towel (a must for cheaper hotels),
sweatpants,
small digital camera (I use an Olympus waterproof, shockproof, 12 MP),
maybe couple pr underwear (probably not cause I haven't worn them in decades except in flightsuits, but a good precaution for chaffing),
can of Cruex (just in case the rawness starts),
1-2 shirts with collars (just to get out of Ts once in a while),
waterproof bag (one came with the Tour Master),
cheap metal knife, fork, spoon,
maps
That's about all that I would need anything else would be a want. I don't even think I've filled my saddlebags yet leaving plenty of room for shit bought along the way. There are creative ways to pack that really economize your space. Anything you must buy on the road costs at least 2-3 times more than at home.
To anyone that's done any 1-3 week backpacking trips alone or with one other person packing a bike, eating bought food, having stores readily available to buy additional items and using hotels makes packing pretty easy. When you are backpacking you cut the handle off your toothbrush to save weight. Carrying a beer to enjoy a week into a hiking trip is a real luxury.
Here's my last 5 day bike camping trip a couple of weeks ago.
I've got everything listed above plus sleeping bag, hiking boots, hiking shorts, cans of food and homemade trail mix, 4 man tent, air mattress, extra helmet (never know who you might meet along the way), additional SLR digital camera, Portuguese-English dictionary, book to read, McBook Pro, folded up backpack in the saddlebags for day hikes, several maps, cigars and some other things I don't remember packed on the bike.
Notice the date at the water point. 1865 As the US Civil War was ending the stones were placed on this water point in rural Portugal. It still provides clean, fresh water for the village as it has for 145 years. These points are all over the country and great places to stop along the old national roads and refresh.
Good luck on your run,
Snake