couple other things that may help.
Since the bedroom is the furthest run, it also likely has the largest temp drop in furnace air temp. Also, the typical ducting is the flimsy corregated stuff which is VERY restrictive to airflow with all the corregations. really disrupts airflow.
My solution
1) drop the underbelly and replace all the ducting with the 4" solid tubing and flex angle joints. the tubing is available in 4' lengths at home improvement stores. comes flat, you roll it up and snap it together
2) wrap each joint (including the lengthwise snap joint) with the aluminum foil tape for this purpose
3) wrap the completed ducting with either fiberglass insulation or the thinner foam insulation with one side adhesive coated, the other side reflective foil.
That made a HUGE improvement in airflow and air temp in our trailer and cut down furnace run time.
there is also one other likely big heat loss section in your bedroom. If your bed is over the top of a passthrough, there is likely NO insulation in that area. just thin plywood. go into the passthrough and use some 1" or so foam core insulation glued to the plywood.
2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!
