We have all seen the YouTube video where the guy retracts the frets via a lever, unfortunately the mechanism doesn't work in practice. We have also seen that bass that is fretted from 1-12 positions and fretless 13+. There is also this Nexus guitar from Poland:

http://www.nexus-guitars.com/images/models/bmmonster/front.jpg

And let's not forget this oddball Rob Allen creation:

http://www.roballenguitars.com/images/info_custom/infocustomslices_46.jpg

I was contemplating purchasing say a used Conklin 7 string off ebay and attempting to make it half fretless.

Now I could go the route of simply removing the frets and putting in shorter frets, so say it would end up 4 strings fretted and 3 fretless. Or another idea is to remove the frets and build up the height of the fretless side by adhering an piece of wood to bring that side up to the same height as the frets will result in. Another idea, but probably not doable is to simply fill between the frets with wood filler and apply a veneer over the radiused base to give a consistant playing surface that is within thousandths of an inch of the fret height.

What makes the most sense?

remove the frets, fill half the slots with veneer, refret the other half

I would think you have two ways of doing this.(if your buying this bass and not building it from scratch) 1. buy a fretted bass. defret it. refret with half frets and half would filler. or 2. buy a fretless. cut fretslots and fret it for only half of the board and leave the other side alone.

The only issue is, the strings will be higher on the fretted side if I follow either of these ideas. I am wondering if this is an issue regarding output via the pickups.

The only issue is, the strings will be higher on the fretted side if I follow either of these ideas. I am wondering if this is an issue regarding output via the pickups.

Using smaller frets, such as banjo or mando frets might help. if you are worried about output, get pickups with adjustable pole pieces, or mount them in such a way that would accomadate for string heighth. or if this bass has a bolt on neck you could make your own neck with an uneven fingerboard. Make the frettless side even with the top of the fret on the frettedside. doesthatmakesense?

or if this bass has a bolt on neck you could make your own neck with an uneven fingerboard. Make the frettless side even with the top of the fret on the frettedside. doesthatmakesense?

That is way beyond my ability.

That is way beyond my ability.

me too!:D Iv always thought this was a cool idea though. I wanted one like this for a while.

what if you got split pickups (think P-bass) then you could set both sides how you want them

WHY?

Just curious.