Ok, this is absolutely a NO GO.
I always try to listen, understand and accommodate mommies' and daddies' needs but, hey, this is just unsafe on too many levels! So pardon me if I may seem a bit too strict.
Here is why we must not perform the forward facing, no matter which support you are using.
1. The straight position overloads the little spine, which instead should always keep the physiological shape (C shape for non walking kids, then developing in synchro with the development of baby's motor skills).
2. When forward facing legs and arms have no support at all, this means that all the weight put pressure on the genitals and hip. The harm is real!!!
3. The solar plexus gets overstimulated instead of being protected from external stimulation.
4. Baby's arms and legs will be hanging out of the carrier in a totally non harmonious way. This shifts the barycentre of the whole couple baby-carrier. To compensate, the person who carriers the baby will tend to arch his/her own spine (wrong posture!) which means:
a. heavier load
c. bigger effort
The list could go on, but to me these are the key points. And it is already enough, isn't it?
It does not make any difference if you are performing the forward facing for a short or long period, especially because it is very personal to define a short period of time, right?
And it is not ok even with the very popular "korean" seat (which by the way should be banned from the market, in my very personal opinion).
It is not ok for you and the baby.
Babywear as long as you can but do it safely!