Hi seemster
Apologies if I wasn't clear.
Oestrogen (alone) stimuates the growth of the endometrium ( womb lining) in a dose dependent manner - more oestrogen = thicker lining. In a sequi HRT regime, progesterone changes the structure of that lining and withdrawal of the progesterone causes it to shed. The degree to which it does this is also dose and duration dependent ie thicker linings need more progesterone and for longer duration to achieve the full effect (ie changing the structure - as I understand).
Therefore, other things being equal, there is likely to be a bigger bleed as a result of higher doses of oestrogen, provided the progesterone dose is sufficient. On higher doses of oestrogen therefore - that extra two days of Utrogestan will help to protect the womb.
Not sure what the difference in bleeds would be with the increase in progesterone by two days, if the oestrogen dose remained the same - but for example increasing the number of days of progesterone per cycle, from say 14 to 21 should eventually result in lighter bleeds, because continuous progesterone (at the right dose to balance the oestrogen) also eventually alters the womb lining in such a way that the oestrogen receptors do not respond to oestrogen and it does not thicken - as in continuous combined HRT, and this will start to happen on a regime of 21/28. The exact biological mechanism is somewhat complex and I dont fully understand it!
Hope this clarifies?
Hurdity x