Adapting this NSC app note for my +150V regulator

Hi all. I have the need for a linear regulator to supply +150V at 0 to
50mA from a 260VDC unregulated input. There's this National app note,
"High Voltage Adjustable Power Supplies", with which you may be
familiar:

http://www.national.com/ms/LB/LB-47.pdf

It seems that using something like, say, TIP50 for Q1 and Q2, and
reducing R3 should do the trick. Is there anything I have overlooked,
though? Regulated power supply design is not my area of expertise.

Thanks in advance,

--Dave in New York

PS: TIP50 data*** "for those wot wanna see it":
http://www.fairchildsemi.com/ds/TI/TIP50.pdf
.