Coupons with free trial time

Hello,

I am looking for a solution that we can offer a free first month on a (monthly) recurring product through using coupons. I know that free trial period works on products, but we want offer the free trial only to a special group of people (by using a coupon?)

100% Discount coupons didnt work right first, because 100% discount (also 100% in equivalent absolute amount) triggers a "free payment" processing and the system was not asking for payment information (paypal or manual banking information).
This problem was fixed by a little hack on signup.php and member.php by amember support. But a new problem occurs now: 100% discount is now calculated for all recurring periods - and paypal answers with an error message

In general it would by fine if coupons support "trial period" options instead or in addition of defining amounts for discounts.

But for now I am looking any solution that I can offer special people a free trial period.

Any ideas?

best regards

where is the trial price and trial period for recurring payments calculated?
it all works fine as discount & is _between_ 0 and 100. If it is 100%, the paypal payment plugin sends no trial period...

I need something like this:

if product_is_recurring and coupon_discount=100% (non recurring coupon) then
set product_1trial_amount=0; product_1trial_period=product_recurr_period; AND product_normal_price=product_price; product_normal_period=product_recurr_period;

I didnt find this in product.php..