You can have the same optical design slightly tweaked and improved by the same lens assembly manufacturer in a different body.
The Borg 90FL is a doublet fluorite, 90mm F5.6, fluorite at the back of the lens assembly and distance between the elements tweaked. Length with a FTF is 38 centimetres and weight with Borg 80mm rings and Dovetail about 2.3 kilos.
Alternatively, these show up at reasonable prices both on CN and AM on a not very infrequent basis.
The design is an excellent compromise in my opinion of portability Vs optical performance. Field curvature is present and can easily be detected on the moon when it fills the eyepiece or with a Nagler 31mm when panning the skies. Contrast is on par with what one would expect from a fluorite doublet (and yes, IMHO there is a clear and detectable difference vs other optical designs).
There is very slight CA in focus on the Lunar limb but does not detract at all from the views. Has shallow depth of field so dual speed Focuser is a must to optimize use. 4.81 degrees TFOV with a Nagler 31mm, 5.58mm exit pupil and 16x magnification. Pair it with a binoviewer and with Pan 24 or Plossl 32mm at native FL you get slightly more than 3 degrees TFOV.
However, despite the glowing comments above, I will state that obviously it does not reach the level of contrast of its longer focal ratio brethren, having compared it to my Tak FC76DC which is a f7.5 doublet fluorite of similar optical design.
If if you want ultraportable, the FC76DS is compact and provides a gentler focal ratio. If you don't mind a bit of extra weight, the FC100 provides a bit of extra aperture at again a nice slow focal ratio. If you want something in the middle which is ultraportable with a wide FOV the TAK90 or Borg 90 will do you fine.
I find that I rarely use mine with 2" eyepieces. 3.09 degrees TFOV, 4.32mm exit pupil and 21x magnification with a Pan 24 are plenty enough for me. I will use a 2" eyepieces only when viewing the Veil, North American Nebula and panning the skies from Scorpio to Cassiopeia in the summer. The luxury of a 2" eyepieces is nice to have, but not essential at such short focal length.
I have yet to compare the FC76 to the Borg 90 on the planets but my viewing experience with each on separate occasions, show that despite the wider aperture of the Borg, it's shorter focal ratio does impact on the views. Specifically, the color saturation of the smaller and slower scope is appreciably better.
I do realize that there is a small difference in the optics design of the Borg Vs the Tak, but I would venture to say that my experience should mirror the experience of Tak owners. Further feedback from owners of the Tak 90 in terms of their viewing experience would be much appreciated!