I think like everyone else has said, its more of a question of why do you want to subject yourself (and body) to the possible damage? With it being a flat course, I think the odds are in your far for completion, but man...idk...you are def going to be in some discomfort for the latter half of the race. Esp if you're last 'serious' training was 3mos ago and you've only being 15hrs(ish) in other disciplines. Cardio will not be the issue and, imo, rarely is. It is more an aspect of muscle fatigue, nutrition, and as you said, mental fortitude. You can possibly 'will' yourself to finish but you may be doing so at some serious costs of your body. 40miles over your former distance, and a distance you actually trained leading up to mind you, yea buddy....you're going to be in some serious nut-kicking experience time.

It's not impossible...but why the hell do you want to do it like that? There is more risk involved than reward, but in the end, it entirely up to you. The flat course will def be an 'advantage' but that is still 24+hrs of being on your feet, constantly moving, and trying to minimize the damage that endurance athletes actively train for to mitigate in the first place.

Again, I think your fitness level is not really the question, you would/will be better than someone off of the couch. But beyond that, unless you have a solid nutrition plan, with experience, an awesome support team, and have awesome conditions for that day...mental fortitude will need to be at beyond normal high and if you have no end goal of other than just 'wanting to'...yea, it is going to be a serious kick in the nuts that will put you down for days, if not weeks, just attempting.

A 40mi delta over your previous 60mi race...that's almost 2/3 more on top of your previous race, which again, you had actively trained for weeks/months. And now, just b/c you have done some bike time and laps in the pool, you think you will be able to replicate the previous experience plus 2/3 more?? Apply common sense man...or don't.

This race ain't specops qual-ing or Delta recruitment, but if you want to prove something, folks like me are not going to stop you. If someone wants to play Russian roulette, that's their choice. B/c 5 out of the 6x times, the odds will be good. So again, is the risk of what you will put your body through really worth versus choosing a race at a later day and actively preparing for it? Up to you.