Removable but some work involved, no welding. I am thinking the same as you. Also I find that every time I build something it gets a little bit better, so maybe the third "longbike" is going to be the perfect one. I`we got friends who needs longbikes but would not try to make one, so I could get rid of the "less perfect ones" that way. Looks like at the moment I have this urge to make longbikes. Got fed up with knitting you see..
