Short strangles EWJ

iShares MSCI Japan Index ETF (EWJ, around $10)
52 week range is 9.15 - 11.63 , but IV is high now(?) so selling strangles looks like:

SELL -10 STRANGLE EWJ 100 JUN 11 9/11 CALL/PUT @2.62 LMT GTC
Break Even Stock Prices 8.38 / 11.62
Max Profit $620.00
Max Loss Infinite
Cost of Trade including commissions credit $2,620.00 - $39.95 = credit $2,580.05
Buying Power Effect ($2,056.00)

And here's the April spread:

SELL -10 STRANGLE EWJ 100 APR 11 9/11 CALL/PUT @2.34 LMT GTC
Break Even Stock Prices 8.66 / 11.34
Max Profit $340.00
Max Loss Infinite
Cost of Trade including commissions credit $2,340.00 - $39.95 = credit $2,300.05
Buying Power Effect ($2,027.00)

And here with OTM options:

SELL -10 STRANGLE EWJ 100 APR 11 11/9 CALL/PUT @.35 LMT GTC
Break Even Stock Prices 8.65 / 11.35
Max Profit $350.00
Max Loss Infinite
Cost of Trade including commissions credit $350.00 - $39.95 = credit $310.05
Buying Power Effect ($1,041.00)

OK, so actually selling OTM has comparable max profit and break-evens, and requires less margin. (Though actually half the margin is provided by premium received.) Plus, the ITM options have huge gamma. For 20 strangles:
Delta is 21.9441 - fairly neutral
Gamma is -813.54109 - this looks like a VERY big number. I think this means that this gains delta rapidly as EWJ falls (and the short Puts go farther ITM), and loses delta rapidly as EWJ rises (as the short Calls go more ITM and the whole position goes negative delta. So before expiration, this works OK with EWJ right between the strikes, but it's on a knife-edge: as EWJ moves, delta really moves against me.
Theta is 18.97265 I like this: gains from time value are big relative to delta.
Vega is -51.76599 - I expect IV to fall, so a negative number is good.