Problem with cost of sales in multi currency sales (OpenERP 6.0 RC1)

My default company currency is set to TWD (Taiwan Dollars) and I have the Anglo-Saxon accounting method installed.

My default sale price list in is TWD and I have a second price list in USD.

When I make a sale using the USD price list:

-The "Account Receivable" account shows the USD value the same as entered on the invoice under "amount currency" and the the "debit" amount in is TWD at the correct amount according to the exchange rate. (This seem to be correct).

-The entries to the "Income Account" account likewise seem correct. The USD value from the invoice shows under the "amount currency" and the "credit" is the correct amount of TWD according to the exchange rate.

-The "Expense Account" (cost of sales) however lists the "cost price" (from the product page (note I'm using "Average Price" for "Costing Method")) as the USD value (the cost price is in TWD as that's the company default) and the "debit" is the cost price (as if it was in USD) exchanged at the exchange rate.

-The "Output Stock" account is likewise affected. The "credit" is the cost price (as if it was in USD) exchanged to TWD at the exchange rate value.

The second 2 entries are not working correctly, however I'm unsure if this is because of the my set up or due to an actual fault. I'll list the translations again below in more detail using actual figures:

Premiss:

Default Currency = TWD

TWD to USD exchange rate = 0.033270

Products "cost price" = 56 TWD (using "Average Price" as the "Costing Method")

Products sale price in USD is $ 2.40

Customer is set to use a pricelist in USD (other then the currency there is no difference between the TWD & USD pricelists)

Sale is for 1 product

Entries:

On Invoicing:

-"Accounts Receivable" account is debited 72.137 ("amount currency" is 2.40 and "currency" is USD) (2.40 / 0.033270 = 72.137) This seems correct to me.

-"Income Account" account is credited 72.137 ("amount currency" is 2.40 and "currency" is USD) (2.40 / 0.033270 = 72.137) This also seems correct to me.

-"Expense Account" account is debited 1683.198 ("amount currency" is 56 and "currency" is USD) (56 / 0.033270 = 1683.198) This isn't correct, it seems like the cost price should not be converted to USD but listed in TWD which is the price cost price and the value of stock is being calculated in.

-"Output Stock" account is credited 1683.198, this seems to be the same problem entry 3.

It seems to me that if the cost of sales and stock value entries need to be calculated in the invoice currency then the cost price first needs to be converted into the secondary currency, for example: (56 (cost price in TWD) * 0.033270 (TWD to USD exchange rate) = 1.863) this value should then be listed as the "amount currency" value and the posted debit or credit should be (1.863 (cost price converted to secondary currency (USD in this case) / 0.033270 (TWD to USD exchange rate) = 56) So it's back to the cost price in the default currency.

I don't have much experience with OpenERP, is this incorrect behavior of the multi-currency accounting entries due to by set up being incorrect? Or perhaps due to a bug in either the Anglo-Saxon accounting module or the multi-currency part of the system?

(Note that I'm using OpenERP 6.0 RC1)