My imo and all...but you should cut the PVC pipe to a specific length based on measurement of the assembly.
With the spring in, spacer/washers out and the fork cap on, measure the space between the top of the spring and the bottom of the cap (rod fully extended). Say it's 90mm. The washers are around 3mm, so if you cut a piece of PVC 97mm long, you'll have 10mm of preload.
Measure each fork and cut to fit. Don't make 'em both the same having measured just one spring. Well, unless you know for sure the springs are exactly the same length.
BTW..make sure the clips on the bottom of the spring came out when you removed the old springs. Re-clip them to the new springs. If you didn't get the clips out with the oem spring..they're still at the bottom of the fork and you have to get them out!
When you reassemble, screw on the top cap by turning the tube, not by turning the cap.
Oil level by a local tuner's figgers is good @ 110 on the kdx. I've generally run 100. It's easier to add some (via the bleeder screws) than it is to take some out.