I have indeed looked and read up on the different positions.

It would just seem to me that the conclusion would be that many traditional Catholics would be in objective mortal sin if they are currently receiving invalid sacraments or attending una cuм Masses.

Also, perhaps some traditionalists take the risk of attendings Masses of a doubtful traditional cleric due to habit or wanting to keep the habit through simulation.

I wanted to simply ask the thoughts of those who are sedevacantists and hardliners on this matter to get a better understanding. 

Kephapaulos,
I do not understand what makes you think it is a sin to attend a Mass una cuм. Exactly what sin is it that you think is being committed - exactly?

Did you not read what +ABL said that I posted earlier? . . . ."It is not said in this prayer that we embrace all ideas that the Pope may have or all the things he may do....We pray for the Pope and all those who practice the Catholic and Apostolic Orthodox faith!"

At any rate, these days we must go where we know the priest and sacraments are valid, never go where we know they are invalid, and where there is doubt we are bound to find out before we receive the sacraments. That's just the way it is these days.

If after due diligence you find out you were wrong and are sure you received invalid sacraments, then don't do that anymore and tell that to the valid priest in confession when you find one and let him be your judge, that's his job. IMO, there is no sin there but that's only IMO, it means nothing, let the priest sort it out.

While IMO there are many doubtfully valid priests out there, I do not think there are very many people, if any, who attend Mass / receive the sacraments from doubtful or invalid priests on purpose.

But if that is the case, then they should never receive the sacraments from those priests. What they need to do is  once or twice a year make the long, long journey to a priest they know for certain is valid and receive the sacraments from him in order to fulfill our yearly obligation to receive communion and go to confession.

That's good that you have researched the positions out there.  I guess I'm just not sure what asking our thoughts would do for you beyond that. I would think that those that post here tend to follow/agree with one of the positions you already researched.  I highly doubt any of us have some unique stand. 

I tend to agree with and trust Bishop Pivarunas on these sorts of matters.  I am hesitant to claim any Traditional Catholic who is trying to survive this mess as being in mortal sin.  I don't think any Traditional Catholic would go to a mass with a priest he/she knows to be certainly invalid.

Outside of the una cuм issue, the only other time I have heard of this idea is from the home alone contingent who believe that ALL traditional masses are illicit without a pope.

I've never heard that, only that none of the traditional clergy have jurisdiction and no miracles to support them.

I'm fairly certain that Home-Aloners believe that the Trad masses are illicit at best (and therefore mortally sinful to attend).

Yep, that's what the ones I knew believed. One family I knew had full access to daily Mass of then Fr. Sanborn less than half a mile away from their home for a long time but did not and would not go.

That's good that you have researched the positions out there.  I guess I'm just not sure what asking our thoughts would do for you beyond that. I would think that those that post here tend to follow/agree with one of the positions you already researched.  I highly doubt any of us have some unique stand. 

I tend to agree with and trust Bishop Pivarunas on these sorts of matters.  I am hesitant to claim any Traditional Catholic who is trying to survive this mess as being in mortal sin.  I don't think any Traditional Catholic would go to a mass with a priest he/she knows to be certainly invalid.

Outside of the una cuм issue, the only other time I have heard of this idea is from the home alone contingent who believe that ALL traditional masses are illicit without a pope.

Thank you and everyone for your responses. I guess I do have the temptation to fall into human respect, but I do admire most of the traditional groups. I would need to respect the rules of certain groups, of course, if I ever attended their chapels. 

I wanted to simply have help and advice in understanding better these issues of validity and una cuм since they touch salvation it seems in principle.