As above, opinions and advantages/disadvantages to both types of chain tensioners on a single speed frame. In terms of eccentric BB's how does Phil Wood fare?
If your starting from zero an external EBB is the most reliable and solid option... (not the lightest though) Paragon slider dropouts have got some good reviews also.
little Groovy talk on the EBB http://groovycycleworks.blogspot.com/20 ... build.html
I've got an EBB on the Seven and it means you can have a normal rear drop out with hanger and still be able to use it as a SS. Also means that you can tweak the seat tube angle a bit and alter the BB height . I also worried about the number of bolts and the amount of aligning and fiddling that would be involved with sliders or slotted to ensure that you got the wheel straight and the disc brake spot on. No worries about that with an EBB. Final thing is it looks so clean as it's all hidden behind the cranks rather than having a Brunel type contraption on the back of the bike.
However the great thing with sliders is that you can change the dropouts to be geared, ss or Rolhoff very quickly and cleanly. Probably the best option is to get an EBB with a replaceable rear hanger dropout so that you can get rid of the hanger when in SS mode but put it back if using gears, rolhoff seam to be sorted with all the speedbones etc if you want to use that at a later point.