My next bass project (and electric upright fretless bass), like my first one, is primarily red oak  it's just easy to find the pieces I need (in the sizes I need) at Home Depot. Red oak is a decent hard wood and I can generally find something straight enough for my purposes. It does have that porous quality that makes it a little hard to use a hand plane on, but so far I've done ok with it.

In the cigar box bass I'm finishing up now, I laminated three 1/2" thick pieces together to form a straight 1 1/2" neck that fit three bass strings nicely. I put no additional fingerboard piece atop this laminated neck - it was straight and fit the purpose well enough.

This time the bass will have four strings and I've already created the neck with a tapered width - 1.5" at the nut going up to 2" at the end of the fingerboard. I'm thinking of using a flat, thin-stock fingerboard atop the laminated neck. I've located a couple possible pieces online. 

First question - How hard is it to add a radius to a fingerboard? I don't have much of a workshop and use mostly hand tools, I'm wondering if I'll be able to modify the fingerboard in a way that doesn't introduce highs/lows that would show up when playing.a fretless instrument.

My second question is this - how thin/thick should this fingerboard be? If I were to go for some amount of radius, this would probably answer itself - I'd need the 1/4" stock in order to have material to shape and I can easily find 1/4" thick stock. But if I stayed with a flat neck,I found a nice looking piece of 1/8" thick stock. Is 1/8" too thin? I'm not worried about the neck warping - the laminated oak should be just fine keeping straight.

Thanks in advance,

Dan