v4 DES option 1 path 2 full performance accounting

I have a Zone 2A 6 story new construction residential dorm building uses ERU DOAS(gas fired(steam not generated on site but campus loop +DES chilled water) that provide outside air to fan coil units with electric heat. the project  has campus central plant for cooling only heating source is onsite fcu with elec heat. I used trace 700 for energy model so individual fcu system is modelled with optional ventilation fan for Outside air and energy recover. proposed  system is chilled water fan coil units with electric heat and hence plant loop is chilled water and electric heat. upstream (campus efficiency modelled) and downstream secondary loop modelled as designed. now baseline system Ashrae 2010 maps to system 2 pthp. according to des path 2 baseline should be modelled as standalone dx coil and heating will be electric heat. if i model this way it will be comparing centralized proposed building with standalone decentralized baseline pthp systems and energy savings are negative. according to Ashrae 90.1-2010 appendix g3.1.1.2 if building uses only purchased chilled water only and not purchased heat then g3.1.1.1a and g3.1.1b shall be used to select the baseline hvac system with modifications listed, in this case system 1 &2 maps to constant volume fan coil units with fossil fuel boilers. so i assigned the pthp cooling coil to chilled water loop and heating coils to fossil fuel boiler.is this modelling approach correct? in both cases upstream and downstream plant is modelled and baseline efficiencies are modelled strictly to appendix g. If i use this approach then i get about 20% savings for proposed. any insight on modelling DES path 2 full performance accounting, this will be helpful.