DirectDraw on WM5/6

We currently have 3 phones we are deploying to - an HTC Dash (WM5), Motorola Q (WM5), and Samsung Blackjack (WM6).
Using openmethod = DOM_DIRECTDRAW and surfacedefault = EST_SYSTEMAPI in the display parameters we are able to get access to a DirectDraw surface through GetSysApiSurface() on the Dash, but on the Q/Blackjack it returns null, suggesting that DirectDraw is not getting used.
What sort of factors aside from the display flags would impact whether DirectDraw is invoked? It's odd that we are getting DD on one WM5 machine but not on the other WM5 or the WM6.
The end goal here is to use the DirectDraw API to render Windows fonts onto an Edge surface - we of course have the fallback of using bitmap fonts but we'd like to avoid them if possible.
Using openmethod = DOM_DIRECTDRAW and surfacedefault = EST_SYSTEMAPI in the display parameters we are able to get access to a DirectDraw surface through GetSysApiSurface() on the Dash, but on the Q/Blackjack it returns null, suggesting that DirectDraw is not getting used.
What sort of factors aside from the display flags would impact whether DirectDraw is invoked? It's odd that we are getting DD on one WM5 machine but not on the other WM5 or the WM6.
The end goal here is to use the DirectDraw API to render Windows fonts onto an Edge surface - we of course have the fallback of using bitmap fonts but we'd like to avoid them if possible.