I got one guy to take a look at my HB42AI and got a similar response. He said biggest would fit is a PE Neo 1.6. I think the same size as the 2700. He would have to run a 6" liner and do some work on the cap. He quoted $4400. A stove would start around $5k. Doesn't seem to have any financial benefit. If I fully replaced my heating it might save about $750/yr; more reasonably looking at $200/year. It would basically be purely for entertainment.
Good luck OP.
Hey! Are you still out there?? What did you end up doing? I think you wanted a wood burner but I want to switch to gas. I have that exact heatilator, HB42AI and want to get a gas direct vent insert installed. I'm having trouble figuring out what's behind that bottom or top vent. The manual for the HB42 only refers to using gas logs but nothing about inserts. Its from 1995 so maybe they weren't a thing. The manuals for the inserts say anything screwed on can be removed such as heat shields but I don't know what's screwed on inside there. I need 24" and the opening height is 20", but I'm pretty sure there isn't anything behind those vents except, well vents. If the bottom can be removed without "cutting" I should be fine. I'm considering a few brands at this time, Mendota ($$$), Jotul, FPX/Lopi and Heat-n-glo. They all pretty much say the same thing. THe FPX 616 install manual does say it may be ok to remove the floor
"CAUTION: Firebox floor removal is not covered under the appliance safety standard (ANSI Z21.88 CSA 2.33)
used in the safety certification of this appliance, however, this method has been tested by Travis Industries and
it has been determined to be safe following the instructions below. Before installing the appliance using this
method, contact the Authority Having Jurisdiction to determine if this installation is acceptable in your area. The
sheet metal base (or metal wrap) of the fireplace must be left in place and a minimum ½” cement board sheet
placed under the entire length and width of the appliance."
the Heat-n-glo says basically the same thing. but the diagram only shows a small piece of floor being being able to be cut.
"The metal floor of the factory-built fireplace may be
removed to facilitate the installation of the insert.
• Cutting of any sheet metal parts of the fireplace in which
the gas fireplace insert is to be installed is prohibited,
except the floor as tested for and as noted above and in
Figure 4.1-B."