Landstrom gives a good description of the size of longships in the Viking era. Each space between deck beams was called a room. Each room comprised a pair of oars. Each oar had one oarsman. He suggests that the crew sat either on loose benches or chests, neither of which are in the ship finds, in that position.
The "old law books" classify the ships as usually 20 rooms, but often twentyfive or 30. Beyond that the very largest Drakkar were 32 or in single instances each 34, 40 and 60! rooms. The distance between oars in the Gokstad ship was 38 1/2" (hats off to the carpenters for accuracy!). The Revell ship is 16 rooms, I believe because it is a second generation copy of the Gokstad ship.
So a ship of 20 rooms was about 100 feet long, and the supposed largest would have been 260 feet long! The Gokstad ship has 16 rooms. The Drakkar might have had 32.
I suspect a great deal of misinformation is involved in all of the actual recreations, except for the several found.
For certain a ship on a raid would not have sailed with shields outboard. These ships could sail and even beat to windward and had no thwarts,a low and working freeboard and would have been quite wet.
The sailors were not normally at the oars, most probably huddled on the higher side of the ship. The excavated ships are full of racks, tent frames and other temporary structures that seem to me to suggest a lot of spar and oar storage.
I cannot find reference at all to ship vs. ship battles. These were shore raids, and as such would probably have been in stealth, not against castles or fortified positions. I personally do not see the need for a shield row as protection. Even in 1066 the Normans landed and did battle on dry land.
I also think that while it is frustrating that we can't find a picture of the Gokstad shields, in all probability they were in the same category as the dogs, horses, kitchen ware, etc. sent to meet Odin with the occupant; more ceremonial than useful.
Landstrom has a beautiful (surely) drawing of a ship under sail, with a wealth of detail. As I mentioned, the beitass is rigged on the lee side to the end of the yard, the sail is a billowy square with leather crosshatch, the lower corners of the sail are belayed fore/ aft, the yard has double rigging, there is a deep single rudder, there is a prominent strake on the stern, an iron anchor over the bow. She has one thwart board, no shields overboard, but also no crew so who can say where he drew the line with his knowledge.
Many of the eighth and ninth century Goteborg stone drawings of Norse ships show a hull with a right angle at the keel to stern and bow posts, at least in overall profile. Which would have been a more stable sailing ship, and I suspect that may have been an added strake feature at least at the stern for longer voyages.
Also he draws some very fine blocks which beggar verbal description but are certainly not what we are accustommed to.
I guess if I were to model a 16 room ship on a raid, I would expect either a ship before the wind at full sail, no prow figures mounted, and the crew taking protection from the weather in a tent at the stern; or, not under sail, under oar, no doubt muffled with sacking, sail struck and the yard stowed, with a raiding party assembled in the middle, armed, helmed and brandishing unlit torches and their shields. And dragon head fitted.