First off I got to thinking about this and maybe your fork springs are too long. Too much spring coils run into each other and it bottoms out too early. Compressing a spring for a long time will not make the spring longer, it will make it not stand as tall. It sounds like someone has swapped springs for whatever reason.
My advice is to get a set of stock OEM springs. You'll still need the preload tubes. You'll need less than a quart for each leg, maybe 20 ozs. I'm not sure about using engine oil because of seal compatability. Use 20w or 10wt fork oil, fill to about 4" from top of tube with fork fully extended when finished. Start slow so you don't overfill pump the forks full travel about 10 times to get air out, then set the 4".
2005 1100 Custom
ORKed 5/16" Lines
PODs K&N RU-600s W/PCV
PCS XXX/2 cams
Jetted & PMS Tweaked 20.0/152.5 3.0 turns
Wimmer Machine Custom Oil Cooler & Stash Tube
Dyna 3000 Step 5/ 6500 redline
6" Fwd Control Extension W/Boards F&R
Memphis Shades Bullet Fairing
Progressive 465 rear
Progressive Springs and GVE front
10,000 Monkeys throwing crap at the glass and this one thinks he's Picasso...