Everyone will have there own opinion of what they like and what works best for them! There are allot of different ways or combinations to run 5 or more rods!!!! you will have to experiment with different set-ups.
I usually get out on Erie, Huron, Ontario 7/8 times a year in up too 5 / 6 different boats!!!! So i have the oportunity to see / try several different setups.
Based on your current setup...ie 4 dipsy's...the easiest way to run extra lines would be (my opinion) add a 10 colour leadcore straight out the back of the boat. once you master 5 rods....take an inline board hook it too the leadcore out the back and send it out the side (dipsys should be deep enough ..not to hook leadcore as it passes over it) ...then send another leadcore out the back and either leave it there or use another inline board and send out the other side.
on huron (port elgin) we usually only run 5 rods (lake is ruff and boat can get turned easily& and we make sharp turns in the humps!)
2 down riggers 30-50' leads, 2 dipsy's (1 each side)100-200' back (depended on season and depth), and 10 colour leadcore straight out the back.
All fish are brought in up the shoot (back of boat, not side) without having tangles or clearing lines. we will move the leadcore to another rod holder usually in the rigger extra holder (opposite side as fish got hooked)
On Ontario...small boats 14-16' usually only have 1 rigger in the boat, so we run it, 2 dipsy's and a 10 colour lead out the back. I have been out without riggers so we ran 2 dipsy's and 2 leadcore off the back corners....have to be carefull when turning as boat is only 5' wide and lines are close together....had rainbows tangle the lead lines twice so went with 3 dipsy's and 1 leadcore..
On Erie (5 different boats and 5 different setups)
Ive done
big boards with 2 leadcores off each side (shower curtain hook & alastic band) and 2 riggers with long leads 100' on occasion the long rigger lead has hooked leadcore during turns. personally havnt caught more than a handfull of walleye off riggers....but lots of other people do!
ive also run dipsy's and inline boards with lead out each side of boat and then another lead core off one back corner and another dipsy off the other too achive 6 rods out
Havnt triied it yet...don't have enough boards.
any other time out with 2 people...4 rods...my go to set up is 1 dipsy off each side of boat....and 8&10 colour leadcores out the back or off inline boards.
In my opinion ...there is no right or wrong ...experiment until you find something that works for you!!!