I'm dealing with the random length issue as well. For a receiver ONLY,
it isn't going to make a lot of difference. However, when you get your
transmitter, you need some sort of matching device (various MFJ units
come to mine), and a SWR bridge of some sort to measure your SWR. If
you get those in the mean time, you can use the matching device to
improve your receiver performance, as you will be matching your
receiver to the antenna. Just tune the matching device for maximum
noise in the band.

If you are just going to be listening, there are a number of active
antenna improvement devices.. basically a matching network and some
sort of amplifier and gain control. Worth looking into.

I have about 1/4 wavelength at 40 meters in my attic, and I can match
it just fine for my QRP rig. What are you planning on for a
transmitter?

/paul
W3FIS