fixed commission per order not items nor units

Hi,
I tried to make certain membership plans have commission type “percentage + fix” (for a free membership plan) and a “percentage only” commission for a payed plan. So I intend to charge this free plan the percentage plus e.g. 1$ for each order.
But with no modification WCFM applies this fixed amount to each single unit bought:
Example for commission of 1$:
3 pcs. product A -> 3* 1$ = 3$
2 pcs. product B -> 2 * 1$ = 2$
Total commission charged is 3$ + 2$ = 5$

In these two threads
https://wclovers.com/forums/topic/commission-settings-not-working-correctly-please-help/
https://wclovers.com/forums/topic/commission-per-order/
you mention two different kind of code snippets as a solution:

add_filter( 'wcfmmp_order_item_quantity', function( $quantity, $product_id, $variation_id, $item_price, $vendor_id, $order_id ) {
	return 1;
}, 50, 6 );

add_filter( 'wcfmmp_is_allow_commission_fixed_per_unit', '__return_false' );

But both end up:
3 pcs. product A -> 1 * 1$
2 pcs. product B -> 1 * 1 $
Total commission charged is 1$ + 1$ = 2$

Is there a way to get for certain membership plans a commission of e.g. 1$ per order not dependent on number of items, units or products?

@Craig: You have this code snippet running – how is your outcome based on the example (1$ or 2$)?