If you can get away with using the same antenna for transmit and receive on MF and LF, count yourself lucky. There are some very successful operators who manage it but they are often based in more remote, RFI quiet locations. Even then, as Carl implies, it's useful to have a few receive options, perhaps including a loop or Beverage, if only to account for propagation variability. For most of us working from more urban locations separate antennas are usually the order of the day. Nevertheless, most of us do set up the T/R switching etc so that we can listen on the transmit antenna if desired.
While there are a lot of local variables, I find modelling of the type shown by Richard to be extremely valuable, if only as a way of underlining some of the inconvenient truths that often get lost in anecdote and in the face of desperation. There's a great deal to be said for getting into the ballpark with a given design, especially at these low frequencies where structures are large and the effort in getting something erected and working can be significant.
With a bit of space and wire available, Trip (OP) could do worse than give the elevated T a go. I'd probably be tempted to increase the height of the vertical section a bit but, regardless, it'd be a good place to start.
73, Peter.