I only have the one 4 string bass to compare the existing 5 neck to: it is 2mm wider at the nut and heel than my 4. I thought it would be worth a look for a fretless 4 neck to fit and convert.
The current spacing at the bridge is 15.5 mm. Not an easy slap bass but for finger style I find it great.
As for string tension I guess if I go for it I'll find out if its too much...
