All the good Hickory boards that I could get full lenght backing laminates from have been used over many years. The ones I have left have about 40 inches lenght of good material. So I was thinking to make a splice in the middle. My question is if anyone have tried to use spliced backings. It is just about impossible to find any good Hickory over here nowadays.

Spliced backings should be just fine with the splice in the middle.  I've done it a couple times, although not with hickory.  I'd make an interlocking splice -- a dovetail would be perfect -- hard to pull off maybe, but perfect.  I've used finger splices assembling all the bits & pieces for a horn/sinew bow...  Anything that gains you wood/glue/wood contact.

Bue, I've spliced hickory backing strips a few times. I've used both a butt splice and a beveled splice and I usually did an overlay to cover the splice. That overlay can be thinned and incorporated in the handle design.