I tested the focusing travel by conducting some experiments:
1. 2" diagonal + 2" eyepiece: coudn't reach focus, still need around 1cm of in-travel, a bad news indeed!!!
2. 1.25" diagonal: it works basically... it reaches focus with my 20mm widescan, with and without 2x barlows; it reaches focus with my 13mm Nagler, so basically, it's a good sign. But there is not much room remain... maybe it won't work with my BF10? I got to test!
Since (1) failed, the motivation to continue the project is much reduced. Of course, if (2) is really do-able, the incentive will be to sell the Borg 45ED II which further consolidates my equipment line up, which is a good thing definitely. However, since the focus travel is around just-make, so whether it will work or not, is pending further testing. Secondly, a reducer couldn't be used most probably, that makes full disc in one shot impossible.
So, not much incentive remains. Since the NGF-S is already very "low profile" and thus, any other focuser is not going to work most probably. Give up?