I have a few questions.
What is the input voltage ,output voltage and what power do You intend to achieve.
Do You need currentmode or is the choice of SG3524 a matter of availability?
You can use the SG3524 for DC-Dc converters in pushpull setup (depending on the inputvoltage)
Personaly i prefer to use mosfets instead of transistors.
Have a look at the following schema (figure 9) **broken link removed**
There is also a decent explanation of how it works.
(please do note the schema they present is voltage mode, there is no resistor that senses the current)
Also keep in mind that the SG3525 has push-pull output and is capable to directly drive mosfets .