Residency application for elderly parents

[power2011]

I would like to get some advice regarding the residency application for my elderly parents. I have done a lot of reading, many relevant posts on this forum, so I guess it's time to get some feedback before going ahead with my application. (I'm planning to apply myself but I hope I can get some consultation with a solicitor, though so far they have refused - they either want to do the whole process £1000, or just talk for 1 hour in general terms, no specifics... !? nothing in between !?)

I list my parents case and what documents I plan or can provide and you tell me what you think:

1- I am a UK citizen the past 10 years, have a very high income. Live alone, never married and no kids. Own a two bed flat (no mortgage).
(Docs: Salary and saving documents and deeds to the flat and some utility bills.)

2- My sister studying PhD at a uni in UK for the last 3 years. I also support her (I can easily afford it !).
(Docs: Letter from her uni, my statement of sending money every months).

3- My brother and her family live in US for the past two years
(Docs: Letter from his condo management and utility bills proving he and his family lived there for the past 2 years)

No other siblings

4- My father 74, mother 64, live back home. Father heart bypass operation and heart attack some years ago, mother had cancer some years ago and both have some other smaller issues (high sugar and blood pressure etc.). Now both stable but need various pills, regular tests and so on. I'm thinking of suggesting I might buy them private medical insurance in UK - again I can afford it)
(Docs: Letters from doctors regarding their medical history.)

5- Father has a small pension (about £300 per month) and an apartment they live in. Mother is housewife, never worked and no income or property.
(Docs: Letter about my father's pension and the deeds to the apartment)

6- As they have depleted their savings over the years, I have been sending them money every month to support them financially, my father's pension is really not sufficient to live on for two people.
(Docs: My bank statement shows money sent, agency receipts that transfered the money and my dad's bank statement showing money arrived - docs available from around Jan this year.)

7- My mother's family live in another town. My father's brother is nearly 80 and his sister also married, both not able to help financially or physically.
(Docs: ?)

8- My parents have been visiting me in UK on various occasions, more recently as they were living alone . So they have received visitor's visa (last 3 times, 2-year visas, last visa obtained Feb. this year). My mother is actually here but she's going back shortly. I want to mention that they are alone in their country and in the last 2/3 years have become dependent on me in every way as my other siblings have moved away. They are old and frail and unable to travel too much and with my busy work schedule I'm unable to visit them regularly. I am very capable of supporting them financially (very high income) and look after them physically (have no family of my own). I will be writing a long letter explaining all this.

If you guys have any suggestions or tips please fire away. I know there are a few holes here and there, but no application is perfect, it's all a questions of higher or lower probabilities. What do you think...!?

Cheers,